Add Vale linter for TUF documentation

[Ayush9026]

Description of issue or feature request:
Add Vale linter for TUF documentation

Current behavior:
Currently, the TUF documentation does not utilize a linter to ensure consistency and quality in the writing style. This can lead to inconsistencies and potential readability issues across different documentation sections.

Expected behavior:
Integrate Vale linter into the TUF documentation workflow to automatically check for style and grammar issues. This will ensure a consistent and high-quality documentation style. The Vale linter should be configured to use a set of rules that align with the TUF project's documentation standards.

[Ayush9026]

/assign @Ayush9026 i will solve this issue.

[lukpueh]

Looks interesting. Haven't used this before. Can you show an example result? E.g. what would it look like for the current README.md?