Fix editorconfig-checker deprecations

[skupjoe]

New Behavior

1. Fix editorconfig-checker config filename format:

$ editorconfig-checker
The default configuration file name .ecrc is deprecated. Use .editorconfig-checker.json instead. You can simply rename it

• See: https://github.com/editorconfig-checker/editorconfig-checker?tab=readme-ov-file#configuration

2. Fix unsupported non-JSON

$ editorconfig-checker
invalid character '/' looking for beginning of object key string

3. Fix deprecated config name

$ editorconfig-checker
The configuration key `SpacesAftertabs` is deprecated. Use `SpacesAfterTabs` instead.

Contrast to Current Behavior

The latest version of editorconfig-checker (3.2.1) fails with errors/deprecation warnings.

Proposed Release Note Entry

Fix editorconfig-checker deprecations

Double Check

• I have read the comments and followed the PR template.
• I have explained my PR according to the information in the comments.
• My PR targets the develop branch.

[skupjoe]

Sorry I based this from release branch but pulled latest develop into it