LibJS: Add TokenType::TemplateLiteral

This is required for template literals - we're not quite there yet, but at
least the parser can now tell us when this token is encountered -
currently this yields "Unexpected token Invalid". Not really helpful.

The character is a "backtick", but as we already have
TokenType::{StringLiteral,RegexLiteral} this seemed like a fitting name.

This also enables syntax highlighting for template literals in the js
REPL and LibGUI's JSSyntaxHighlighter.

Libraries/LibJS/Parser.cpp

@@ -1037,6 +1037,7 @@ bool Parser::match_expression() const
     return type == TokenType::BoolLiteral
         || type == TokenType::NumericLiteral
         || type == TokenType::StringLiteral
+        || type == TokenType::TemplateLiteral
         || type == TokenType::NullLiteral
         || type == TokenType::Identifier
         || type == TokenType::New