syntax/json: Add comment support to the syntax highlighting

[JoeKar]

This feature already has a quite long story:

• Allow comments prefixed by "//" in settings.json and bindings.json #266
• Feature Request: allow c++-style comments in your JSON files #2701
• Set json syntax highlighting to jsonc #2704
• allow comments in JSON #2736
• cannot add comments to bindings.json, it's rewritten and comments are removed #2995

Since micro already uses json5 to parse his own internal json configurations and we changed the default behavior of the comment plugin to set // as the default comment type within json via #3388 it's just a logical step to highlight it correctly in json's (reused #2736). It was and it will be up to the user if he/she places comments with micro in json, because he/she should know if the file is parsed with a json5 parser or not.
Especially since #3343 it's much more easy to edit micro's own configurations in micro itself by just reloading the changed files. As long as set, reset, bind and unbind (hopefully I didn't forget anything) isn't used micro doesn't rewrite the settings by his own and the comments are kept.

Additionally we can think about adding hjson (#2203) and jsonc (#2704) to the same json syntax definition, instead of creating new file types. The latter one is arguable, since via syntax includes it's also easy to extend/override definitions.

[JoeKar]

Adding hjson to json seems to go too far, since # (supported as comment in hjson) is not allowed by a json5 parser. So #2203 is still valid, but can be reduced afterwards.
Most probably it's the same for jsonc, which allows unquoted values.

For now we keep the PR as is and maybe consider the rest afterwards.