📎 Add a guide to explain how biome behaves with *known* files

[ematipico]

Description

This is a follow-up of the discussion that happened in #237

The task is to create a new guide page called "Biome's behaviour" (or something similar). The purpose of this page is to list all those particular behaviours/assumptions that Biome does that aren't currently documented, or they are but in the wrong section.

Here's the list of things we should do:

1. Move the following paragraphs in this new page:

biome/website/src/content/docs/reference/configuration.mdx

Lines 13 to 65 in e6c12c0

	# Configuration
	The configuration file is considered **optional**, Biome has good defaults. Use the configuration
	file to change those defaults.
	The Biome configuration file is named `biome.json` and should be placed in the root directory of your project. The root
	directory is usually the directory containing your project's `package.json`.
	Here's an example:
	<CodeBlockHeader filename="biome.json" />
	```json
	{
	"formatter": {
	"enabled": true,
	"indentStyle": "tab",
	"lineWidth": 120
	},
	"linter": {
	"enabled": false
	}
	}
	```
	This configuration file enables the formatter and sets the preferred indent style and width. The linter is disabled.
	## Configuration file resolution
	Biome uses auto discovery to find the nearest `biome.json` file. It starts looking for `biome.json` in the current
	working directory, and then it starts looking in the parent directories until:
	- it finds a `biome.json` file;
	- it applies Biome's defaults if **no `biome.json` is found**;
	Here's an example:
	```
	└── app
	├── backend
	│ ├── package.json
	│ └── biome.json
	└── frontend
	├── legacy
	│ └── package.json
	├── new
	│ └── package.json
	└── biome.json
	```
	- biome commands that run in `app/backend/package.json` will use the configuration file `app/backend/biome.json`;
	- biome commands that run in `app/frontend/legacy/package.json` and `app/frontend/new/package.json`
	will use the configuration file `app/frontend/biome.json`;

2. Explain that package.json, package-lock.json, tsconfig.json and jsconfig.json are currently ignored by Biome because the tools that own these files usually apply their formatting/style, and Biome doesn't want to disrupt them. This means that no diagnostics will be ever emitted by Biome for those files.
3. Add a heading that explains the "known" files. These files are listed here:

biome/crates/biome_service/src/file_handlers/mod.rs

Lines 48 to 64 in e6c12c0

	pub(crate) const ALLOWED_FILES: &'static [&'static str; 15] = &[
	"typescript.json",
	"tsconfig.json",
	"jsconfig.json",
	"tslint.json",
	"babel.config.json",
	".babelrc.json",
	".ember-cli",
	"typedoc.json",
	".eslintrc.json",
	".eslintrc",
	".jsfmtrc",
	".jshintrc",
	".swcrc",
	".hintrc",
	".babelrc",
	];

And we should explain that when Biome analyses these files, they are parsed as **JSON files** with `json.parser.allowComments` and `json.parser.allowTrailingCommas` set to `true`. This is because editor tools like VSCode treat them like this.

As a bonus, we should remove `tsconfig.json` and `jsconfig.json` from that list (in the rust file)

[TheShiveshNetwork]

Can you assign this to me? I'm interested in working on this.

[Conaclos]

Assigned :)

[TheShiveshNetwork]

@ematipico check out #624 and do let me know if it needs improvements.