Fix typos in documentation and comments

[Pricstas]

This pull request corrects minor typographical errors in documentation and comments across several files. Specifically, the following changes were made:

• Replaced instances of "a empty" with "an empty" in comments and documentation in cache_store.rs.
• Corrected "a endpoint" to "an endpoint" in contacts.rs documentation.
• Fixed the use of "a error message" to "an error message" in error.rs.
• Minor adjustments to wording in scratchpad.rs for clarity.

These changes improve the clarity and correctness of the documentation.

Related Issue:

Fixes typos in documentation.

Type of Change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist:

• I have read the contributing guidelines.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have updated the documentation accordingly.
• I have followed the conventional commits guidelines for commit messages.
• I have verified my commit messages with commitlint.

[maqi]

Hi, @Pricstas ,

Thank you very much for your contribution.

However, seems the commit msgs themselves got complained by the CI checks.

Could you please squash the commits into one, and make commit title to be:
fix(doc): resolve couple of typos

Thx in advance

ps. you can just use following git cmds to do the squash and re-commit:
git reset --soft HEAD~5
git commit -a -m "fix(doc): resolve couple of typos"
git push --force git@github.com:Pricstas/autonomi.git fix/typos

[maqi]

Hi, @Pricstas ,

I've force pushed to your branch to squash the commits into one and resolve the commit msg errors.