WIP: Improved syntax highlighting in the Web IDE

What does this MR do?

This brings improved syntax highlighting into the Web IDE by using the textmate library that VSCode uses. This allows for the full textmate grammars to be used through web assembly, creating much nicer highlighted files.

However, web assembly isn't supported in IE11 so we fall back to the old way of highlighting.

This also supports Vue highlighting out of the box with no extra configuration or packages needed.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52105

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides