[Monaco]Improve .gitignore definition (#33263)

* Update gitignore.js

* Update gitignore.js

* Add custom color for negations

* Add custom color for negations

* Regex refactoring

* Regex refactoring again

* Move customTokenColors to a separate file

* Move customTokenColors to a separate file

* Update devdocs

* Use kebab case for token names

* Update negation color

* Update index.html formatting

src/common/FilePreviewCommon/Assets/Monaco/customLanguages/gitignore.js

@@ -5,8 +5,8 @@
         tokenizer: {
             root: [
                 [/^#.*$/, 'comment'],
-                [/^\s*!.*/, 'invalid'],
-                [/^\s*[^#]+/, "tag"]
+                [/.*((?<!(^|\/))\*\*.*|\*\*(?!(\/|$))).*/, 'invalid'],
+                [/((?:^!\s*(?:\\\s|\S)+)?)((?:^\s*(?:\\\s|\S)+)?)((?:\s+(?:\\\s|\S)+)*)/, ['custom-gitignore.negation', 'tag', 'invalid']]
             ]
         }
     };