Re-organize and complete documentation

[LoicPoullain]

Issue

The documentation needs better structure. Some parts still need to be updated to v3.

Note: this might break SEO for some time.

Solution and steps

• [x] Update the documentation on the Context class.
• [x] Remove TSLint mention which were removed more than 2 years ago.
• [x] Remove docs on root imports and VSCode which are not related to how the framework works.
• [x] Re-organize the documentation

Checklist

• [x] Add/update/check docs (code comments and docs/ folder).
• [x] Add/update/check tests.
• [x] Update/check the cli generators.

[codecov-commenter]

Codecov Report

Base: 98.86% // Head: 98.86% // No change to project coverage :thumbsup:

Coverage data is based on head (00bcee9) compared to base (a40d6af). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1188 +/- ## ======================================= Coverage 98.86% 98.86% ======================================= Files 96 96 Lines 1667 1667 Branches 388 388 ======================================= Hits 1648 1648 Misses 19 19 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FoalTS). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FoalTS)

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