server : add themes + favicon (#6848)

* Added themes support with two sample themes and a favicon.

* Newline

* Newline

* Newline

* Trailing whitespace

* Increased opacity for contrast

* Increase opacity.

Check actions cancelled for some other priority job and I can't seem to manually re-run them, so MOAR OPACITY

* Opacity action trigger.

Trying to re-trigger the cancelled action.

* One more opacity adjustment

This Actions pipeline is failing for random issues.

* Delete examples/server/themes/buttons_top/completion.js

This will be served from the static string built-in to server.

* Delete examples/server/themes/buttons_top/index.js

This will be served from the static string built-in to server.

* Delete examples/server/themes/wild/completion.js

This will be served from the static string built-in to server.

* Delete examples/server/themes/buttons_top/json-schema-to-grammar.mjs

This will be served from the static string built-in to server.

* Delete examples/server/themes/wild/index.js

This will be served from the static string built-in to server.

* Delete examples/server/themes/wild/json-schema-to-grammar.mjs

This will be served from the static string built-in to server.

* Replaced underscore.