feat(sage-monorepo): validate and format JSON files with ESLint-Prettier

[tschaffter]

Closes #2789

Description

Currently, JSON files are formatted on save in VS Code using the Prettier extension for VS Code. However, we currently don't have a solution to format these files using a CLI. This is required if we want to validate these files via git hooks and the CI/CD workflow.

The solution explored in this PR is to validate and format JSON, JSONC and JSON5 files with ESLint, which delegate the validation and formatting to Prettier. The solution should also work well in VS Code with live validation and formatting on save.

Changelog

• Update VS Code settings to validate and format JSON, JSONC and JSON5 files with ESLint
• Configure ESLint to validate JSON, JSONC and JSON5 files with Prettier
• Remove .eslintignore (deprecated)

References

• https://eslint.org/docs/latest/use/configure/ignore-deprecated

Notes

The root .eslintrc.json has the following line:

"ignorePatterns": ["**/*"],

This prevents ESLint from linting files in the root folder. This instruction needs to be inversed in an .eslintrc.json of a folder so that ESLint validate its content (recursively).

E.g., libs/agora/services/.eslintrc.json starts with:

{
  "extends": ["../../../.eslintrc.json"],
  "ignorePatterns": ["!**/*"],

This change enable to include the root folder but nothing else (see this comment):

{
  "root": true,
  "ignorePatterns": ["**/*", "!/*"],

[tschaffter]

Replaced by #2793