docs(xo-core): update guidelines

[OlivierFL]

Description

• Update guidelines used to create and maintain Vue.js components in web-core, XO 6 and XO Lite
• Split and re-organize markdown files

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes #007, See xoa-support#42, See https://...)
  • If bug fix, add Introduced by
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

Review process

This 2-passes review process aims to:

• develop skills of junior reviewers
• limit the workload for senior reviewers
• limit the number of unnecessary changes by the author

1. The author creates a PR.
2. Review process:
   1. The author assigns the junior reviewer.
   2. The junior reviewer conducts their review:
      • Resolves their comments if they are addressed.
      • Adds comments if necessary or approves the PR.
   3. The junior reviewer assigns the senior reviewer.
   4. The senior reviewer conducts their review:
      • If there are no unresolved comments on the PR → merge.
      • Otherwise, we continue with 3.
3. The author responds to comments and/or makes corrections, and we go back to 2.

Notes:

1. The author can request a review at any time, even if the PR is still a Draft.
2. In theory, there should not be more than one reviewer at a time.
3. The author should not make any changes:
   • When a reviewer is assigned.
   • Between the junior and senior reviews.

[MathieuRA]

Suggested change

	icon(): any
	icon?(): any

[ByScripts]

What would you think of moving "❌ Bad" and "✅ Good" inside the code block for single line examples?

Suggested change

	- Avoid using a single letter or non-meaningful names for variables:
	❌ Bad
	```ts
	const m = 'foo'
	```
	✅ Good
	```ts
	const message = 'foo'
	```
	- If the variable is an array of items, use plural for the variable naming:
	❌ Bad
	```ts
	const vm: VM[] = []
	```
	✅ Good
	```ts
	const vms: VM[] = []
	```
	- When iterating over arrays, use a meaningful name for each item:
	❌ Bad
	```ts
	vms.map(item => item.id)
	```
	✅ Good
	```ts
	vms.map(vm => vm.id)
	```
	- Avoid using a single letter or non-meaningful names for variables:
	```ts
	// ❌ Bad
	const m = 'foo'
	// ✅ Good
	const message = 'foo'
	```
	- If the variable is an array of items, use plural for the variable naming:
	```ts
	// ❌ Bad
	const vm: VM[] = []
	// ✅ Good
	const vms: VM[] = []
	```
	- When iterating over arrays, use a meaningful name for each item:
	```ts
	// ❌ Bad
	vms.map(item => item.id)
	// ✅ Good
	vms.map(vm => vm.id)
	```