custom data source support for modern/legacy projects

[lifeart]

In general, we need to have "simple" autocomplete or resolution logic improvements for our users.

Best way to do it - have special file, with useful information and notations

like: https://github.com/Microsoft/vscode-css-languageservice/blob/main/docs/customData.md

we could figure out way to configure same files for uELS

related issue #151

[lifeart]

shema:

{
 "version": 1,
 "registry": {
    "components": {
       "my-component": {
          "description": "foo-bar",
          "arguments": {
              "age": {
                  "description": "user age",
               }
           }
       }
    }
 }
}