JavaScript JSON mode

CodeMirror JavaScript mode supports additional configuration options, allowing to display json, json-ld and typescript ([doc](https://codemirror.net/5/mode/javascript/))

I need the JSON mode, not sure how this could be configured right now.

CodeMirror supports using mime types as mode values, and then it automatically maps to correct mode, setting `application/json` is internally replaced with `json: true, mode: javascript` but setting mime type in the plugin config does not works correctly as it tries to load a js file `mode/application/json.js` that actually is not there.

This could be fixed by using the same mode resolving logic that CodeMirror has - https://github.com/codemirror/codemirror5/blob/e84384b4210bc35300994de07c6333666f2a5c9e/src/modes.js#L20C1-L20C1 and https://github.com/codemirror/codemirror5/blob/e84384b4210bc35300994de07c6333666f2a5c9e/mode/javascript/javascript.js#L953

Start by tracing how the plugin config resolves and loads a mode when given a MIME type. Compare that behavior with CodeMirror’s src/modes.js and mode/javascript/javascript.js logic for application/json; done means JSON, JSON-LD, and TypeScript modes resolve without attempting to load a nonexistent mode/application/json.js file.

Written by the indexing model from the issue text.