LibJS: Unify syntax highlighting

So far we have three different syntax highlighters for LibJS:

- js's Line::Editor stylization
- JS::MarkupGenerator
- GUI::JSSyntaxHighlighter

This not only caused repetition of most token types in each highlighter
but also a lot of inconsistency regarding the styling of certain tokens:

- JSSyntaxHighlighter was considering TokenType::Period to be an
  operator whereas MarkupGenerator categorized it as punctuation.
- MarkupGenerator was considering TokenType::{Break,Case,Continue,
  Default,Switch,With} control keywords whereas JSSyntaxHighlighter just
  disregarded them
- MarkupGenerator considered some future reserved keywords invalid and
  others not. JSSyntaxHighlighter and js disregarded most

Adding a new token type meant adding it to ENUMERATE_JS_TOKENS as well
as each individual highlighter's switch/case construct.

I added a TokenCategory enum, and each TokenType is now associated to a
certain category, which the syntax highlighters then can use for styling
rather than operating on the token type directly. This also makes
changing a token's category everywhere easier, should we need to do that
(e.g. I decided to make TokenType::{Period,QuestionMarkPeriod}
TokenCategory::Operator for now, but we might want to change them to
Punctuation.

Libraries/LibJS/Token.cpp

@@ -35,9 +35,9 @@ namespace JS {
 const char* Token::name(TokenType type)
 {
     switch (type) {
-#define __ENUMERATE_JS_TOKEN(x) \
-    case TokenType::x:          \
-        return #x;
+#define __ENUMERATE_JS_TOKEN(type, category) \
+    case TokenType::type:                    \
+        return #type;
         ENUMERATE_JS_TOKENS
 #undef __ENUMERATE_JS_TOKEN
     default:
@@ -51,6 +51,24 @@ const char* Token::name() const
     return name(m_type);
 }
 
+TokenCategory Token::category(TokenType type)
+{
+    switch (type) {
+#define __ENUMERATE_JS_TOKEN(type, category) \
+    case TokenType::type:                    \
+        return TokenCategory::category;
+        ENUMERATE_JS_TOKENS
+#undef __ENUMERATE_JS_TOKEN
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+TokenCategory Token::category() const
+{
+    return category(m_type);
+}
+
 double Token::double_value() const
 {
     ASSERT(type() == TokenType::NumericLiteral);