chore: add root tsconfig

[wemeetagain]

Description

• Resolves Linting support in vscode #2095

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[maschad]

Thanks!

[achingbrain]

This is the wrong solution.

• The VSCode eslint plugin is now loading config from the root of the repo, this means any per-package linting config is ignored (not that we should have any, but still - the vscode plugin potentially applies different rules to aegir lint which is chaos).
• It only lints /packages/**/*.ts, this ignores the examples and the multidim tests.

The proper solution is to add "project": true to eslintConfig.parseOptions in each package.json - this will cause the eslint plugin to search for the closest tsconfig.json to the file being linted instead of using a global one in the root of the project.

Refs:

• Feature request: support looking up tsconfig.json relative to linted file typescript-eslint/typescript-eslint#101
• feat(typescript-estree): allow specifying project: true typescript-eslint/typescript-eslint#6084
• https://typescript-eslint.io/blog/parser-options-project-true

[achingbrain]

See: #2122