Add Vale Linter for Documentation Quality Checks

[Ayush9026]

Description:

To ensure the quality and consistency of our documentation, we propose adding the Vale linter to the in-toto documentation repository. Vale is a highly customizable, syntax-aware linter that helps enforce writing style guides and catch common documentation issues.

Benefits:

Improved documentation quality and consistency.
Automated checks for common documentation issues.
Clear guidelines for contributors, helping maintain high standards.

[Ayush9026]

/assign @Ayush9026 i will solve this.