Add separate article documenting TypeScript style guide

[web-padawan]

Description

Depends on vaadin/eslint-config-vaadin#44

Once we finish working on eslint-config-vaadin and integrate it to our projects, we can start recommending it.

1. Create a new article about TypeScript code style, documenting how to use the new config,
2. Update getting started guide (at least for Hilla) to recommend setting up ESLint via CLI,
3. Update existing guides as necessary to mention eslint dev dependency (also for Hilla),
4. Recommend using ESLint for addon authors, with an example e.g. vanilla-colorful etc.

Note, this issue isn't only for hilla branch, because the new config might be also useful for Flow LitTemplate.