LibGUI: Add Javascript syntax highlighter

Author: https://github.com/oriko1010
Commit: 196352ef67
Pull-request: https://github.com/SerenityOS/serenity/pull/1435

Libraries/LibGUI/JSSyntaxHighlighter.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <LibGUI/SyntaxHighlighter.h>
+
+namespace GUI {
+
+class JSSyntaxHighlighter final : public SyntaxHighlighter {
+public:
+    JSSyntaxHighlighter() {}
+    virtual ~JSSyntaxHighlighter() override;
+
+    virtual bool is_identifier(void*) const override;
+    virtual bool is_navigatable(void*) const override;
+
+    virtual SyntaxLanguage language() const override { return SyntaxLanguage::Javascript; }
+    virtual void rehighlight() override;
+
+protected:
+    virtual Vector<MatchingTokenPair> matching_token_pairs() const override;
+    virtual bool token_types_equal(void*, void*) const override;
+};
+
+}