Add rules for JSON file formatting in eslint

[offtherailz]

Description

• Reformat all the JSON files (also deprecating some hardly understandable things like "strings or object format" in localConfig.json plugin)
• Update eslint config to enforce JSON files formatting

What kind of improvement you want to add? (check one with "x", remove the others)

• [ ] Minor changes to existing features
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

Other useful information

[MV88]

@offtherailz currently eslint rules are ignored as explained in the following PR description so if you want to do this, i suggest to take a decision on this

• https://github.com/geosolutions-it/MapStore2/pull/9188

[MV88]

blocked by https://github.com/geosolutions-it/MapStore2/issues/9190