Improve Sail code formatting and syntax highlighting

[AlfredoRodrigues4]

The Sail code in the RISC-V manuals suffers from poor readability and alignment issues. I discovered a repository (https://github.com/Alasdair/asciidoctor-sail) that offers a solution to enhance the presentation of Sail code by aligning it and highlighting keywords with colors. This approach significantly improves the clarity of the Sail code in the manual.
To implement this, it's necessary to add a folder to the RISC-V ISA manual repository with the Ruby files that will handle the formatting. While not all of these files may be useful immediately, for now in simple sail codes only highlighter.rb file is used, they could be valuable for future enhancements.
I noticed that @wmat has previously interacted with this repository, which raises the question of why this solution hasn't been added yet.

And this is how the sail code will look like in the manual.
To implement this improvement, it will be necessary to include these files in the "REQUIRES" section of the Makefile in the RISC-V ISA Manual.

[wmat]

I'm confused. Is this PR adding the asciidoctor-sail extension that Alasdair wrote directly to the docs-resources?

[AlfredoRodrigues4]

I didn't know that you were currently working on the Alasdair repository, I saw it and thought it would be interesting to try to add it to the main manual in order to improve it and try to do something cool, I already talked to you in riscv/riscv-isa-manual#1608 and I already understood the final objective, gonna close this PR, thanks!