Adding a Computer Architecture Book. (#11121)
## What does this PR do?
Add resource(s)
## For resources
### Description
Adding a Computer Architecture Book.
### Why is this valuable (or not)?
### How do we know it's really free?
Licence: Creative Commons Attribution 4.0 License.
### For book lists, is it a book? For course lists, is it a course? etc.
It's a book.
## Checklist:
- [ :white_check_mark: ] Read our [contributing guidelines](https://github.com/EbookFoundation/free-programming-books/blob/main/docs/CONTRIBUTING.md).
- [ :white_check_mark: ] [Search](https://ebookfoundation.github.io/free-programming-books-search/) for duplicates.
- [ :white_check_mark: ] Include author(s) and platform where appropriate.
- [ :white_check_mark: ] Put lists in alphabetical order, correct spacing.
- [ :white_check_mark: ] Add needed indications (PDF, access notes, under construction).
- [ :white_check_mark: ] Used an informative name for this pull request.
## Follow-up
- Check the status of GitHub Actions and resolve any reported warnings!
Francesco