LibWeb: Rename "identifier" and "ValueID" to "Keyword" where correct

For a long time, we've used two terms, inconsistently:
- "Identifier" is a spec term, but refers to a sequence of alphanumeric
  characters, which may or may not be a keyword. (Keywords are a
  subset of all identifiers.)
- "ValueID" is entirely non-spec, and is directly called a "keyword" in
  the CSS specs.

So to avoid confusion as much as possible, let's align with the spec
terminology. I've attempted to change variable names as well, but
obviously we use Keywords in a lot of places in LibWeb and so I may
have missed some.

One exception is that I've not renamed "valid-identifiers" in
Properties.json... I'd like to combine that and the "valid-types" array
together eventually, so there's no benefit to doing an extra rename
now.

Meta/Lagom/Tools/CodeGenerators/LibWeb/GenerateCSSKeyword.cpp

@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022-2024, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "GeneratorUtil.h"
+#include <AK/SourceGenerator.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/ArgsParser.h>
+#include <LibMain/Main.h>
+
+ErrorOr<void> generate_header_file(JsonArray& keyword_data, Core::File& file);
+ErrorOr<void> generate_implementation_file(JsonArray& keyword_data, Core::File& file);
+
+ErrorOr<int> serenity_main(Main::Arguments arguments)
+{
+    StringView generated_header_path;
+    StringView generated_implementation_path;
+    StringView json_path;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(generated_header_path, "Path to the Keyword header file to generate", "generated-header-path", 'h', "generated-header-path");
+    args_parser.add_option(generated_implementation_path, "Path to the Keyword implementation file to generate", "generated-implementation-path", 'c', "generated-implementation-path");
+    args_parser.add_option(json_path, "Path to the JSON file to read from", "json-path", 'j', "json-path");
+    args_parser.parse(arguments);
+
+    auto json = TRY(read_entire_file_as_json(json_path));
+    VERIFY(json.is_array());
+    auto keyword_data = json.as_array();
+
+    auto generated_header_file = TRY(Core::File::open(generated_header_path, Core::File::OpenMode::Write));
+    auto generated_implementation_file = TRY(Core::File::open(generated_implementation_path, Core::File::OpenMode::Write));
+
+    TRY(generate_header_file(keyword_data, *generated_header_file));
+    TRY(generate_implementation_file(keyword_data, *generated_implementation_file));
+
+    return 0;
+}
+
+ErrorOr<void> generate_header_file(JsonArray& keyword_data, Core::File& file)
+{
+    StringBuilder builder;
+    SourceGenerator generator { builder };
+    generator.append(R"~~~(
+#pragma once
+
+#include <AK/StringView.h>
+#include <AK/Traits.h>
+
+namespace Web::CSS {
+
+enum class Keyword {
+    Invalid,
+)~~~");
+
+    keyword_data.for_each([&](auto& name) {
+        auto member_generator = generator.fork();
+        member_generator.set("name:titlecase", title_casify(name.as_string()));
+
+        member_generator.append(R"~~~(
+    @name:titlecase@,
+)~~~");
+    });
+
+    generator.append(R"~~~(
+};
+
+Optional<Keyword> keyword_from_string(StringView);
+StringView string_from_keyword(Keyword);
+
+// https://www.w3.org/TR/css-values-4/#common-keywords
+// https://drafts.csswg.org/css-cascade-4/#valdef-all-revert
+inline bool is_css_wide_keyword(StringView name)
+{
+    return name.equals_ignoring_ascii_case("inherit"sv)
+        || name.equals_ignoring_ascii_case("initial"sv)
+        || name.equals_ignoring_ascii_case("revert"sv)
+        || name.equals_ignoring_ascii_case("unset"sv);
+}
+
+}
+
+)~~~");
+
+    TRY(file.write_until_depleted(generator.as_string_view().bytes()));
+    return {};
+}
+
+ErrorOr<void> generate_implementation_file(JsonArray& keyword_data, Core::File& file)
+{
+    StringBuilder builder;
+    SourceGenerator generator { builder };
+
+    generator.append(R"~~~(
+#include <AK/Assertions.h>
+#include <AK/HashMap.h>
+#include <LibWeb/CSS/Keyword.h>
+
+namespace Web::CSS {
+
+HashMap<StringView, Keyword, AK::CaseInsensitiveASCIIStringViewTraits> g_stringview_to_keyword_map {
+)~~~");
+
+    keyword_data.for_each([&](auto& name) {
+        auto member_generator = generator.fork();
+        member_generator.set("name", name.as_string());
+        member_generator.set("name:titlecase", title_casify(name.as_string()));
+        member_generator.append(R"~~~(
+    {"@name@"sv, Keyword::@name:titlecase@},
+)~~~");
+    });
+
+    generator.append(R"~~~(
+};
+
+Optional<Keyword> keyword_from_string(StringView string)
+{
+    return g_stringview_to_keyword_map.get(string);
+}
+
+StringView string_from_keyword(Keyword keyword) {
+    switch (keyword) {
+)~~~");
+
+    keyword_data.for_each([&](auto& name) {
+        auto member_generator = generator.fork();
+        member_generator.set("name", name.as_string());
+        member_generator.set("name:titlecase", title_casify(name.as_string()));
+        member_generator.append(R"~~~(
+    case Keyword::@name:titlecase@:
+        return "@name@"sv;
+        )~~~");
+    });
+
+    generator.append(R"~~~(
+    default:
+        return "(invalid CSS::Keyword)"sv;
+    }
+}
+
+} // namespace Web::CSS
+)~~~");
+
+    TRY(file.write_until_depleted(generator.as_string_view().bytes()));
+    return {};
+}