Update README

Clear and concise description of the problem

Our current README doesn't provide enough information on how to work with the extension.

Suggested solution

Add several new sections:

• How to run a test
• How to enable/disable continuous mode and its benefits
• How to run code with coverage. Mention that coverage is disabled unless you specifically press the coverage button
• How to debug a test. Mention that if debugging multiple tests, they will not be running in parallel
  • How to use breakpoints/debugger statement
• How to work with test filters (like @open)
• Explain how the extension finds test files (scans for configs and starts new Vitest process for every config)
• Explain how the extension collects tests (it runs Vitest in collect mode, so it can take a while if your tests have a lot of imports)
• Available configuration with description and examples (maybe in a table form?)

I would also like to rewrite the introduction section:

• Remove the current GIF since it uses the previous extension.
• Remove the VSCode + Vitest logo as it takes a lot of space for nothing

It should look something like this:

# Vitest for VS Code

<!-- short description about what this is -->
<!-- table of content -->
<!-- small promo image showing a test file -->

## Requirements

<!-- list of requirements -->

## Feature 1
## Feature 2
...

All screenshots need to use the same project that should be pushed to the repository so we can reshoot it if needed. All screenshots need to have the same VS Code theme. Ideally, screenshots should have a border with a shadow (like on Mac OS) - this is just my preference 😄

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by reviewing the current README and the extension behavior described in the issue. Update the README with the requested usage, debugging, filtering, test-discovery, collection, and configuration sections, and replace the outdated introduction and screenshots. Done means the documented workflows and configuration examples are complete and the screenshots use one consistent project and VS Code theme.