Make auto-completion by schame to work with non-valid JSONs

This issue is a continue of #968 which was implemented on change #1435

The current implementation is limited to work only with valid JSONs, as described in the change request comment.

This is a hard limitation, as usually we want to have the auto-complete suggestions while editing the JSON, and it is likely to be a non-valid while typing its content.

There has being some suggestions how to resolve it:

1. straight forward approach:  try to figure out the missing part and fix it on-the-fly, like removing/fixing the current line and try again - this might not cover every use case but might be sufficient for most of the common use cases
2. use external packages like jsonrepair or partial-json-parser to repair/parse the non-valid JSON - this might be challenging as it might not be aligned wit the current cursor location on the document, so the result can be wrong suggestions
3. find a way to Integrate with the ACE editor JSON parser, and perhaps use the internal AST to understand the current path of the cursor location