doc: Contributing tools/checkpatch.sh example update.

[cederom]

Summary

• Add ./tools/checkpatch.sh -c -u -m -g HEAD~...HEAD example to match checks performed by our CI.
• Add cross-reference to checkpatch.sh documentation.

Impact

• Documentation: adds more broad example of checkpatch verification before PR is submitted to match parameters used by our CI (including codespell and encoding).

Testing

% uname -a
FreeBSD hexagon 14.4-RELEASE-p1 FreeBSD 14.4-RELEASE-p1 GENERIC amd64

% cd Documentation
% pipenv shell
(Documentation) hexagon% gmake html
Removing everything under '_build'...
Running Sphinx v6.2.1
myst v3.0.1: MdParserConfig(commonmark_only=False, gfm_only=False, enable_extensions=set(), disable_syntax=[], all_links_external=False, links_external_new_tab=False, url_schemes=('http', 'https', 'mailto', 'ftp'), ref_domains=None, fence_as_directive=set(), number_code_blocks=[], title_to_header=False, heading_anchors=0, heading_slug_func=None, html_meta={}, footnote_transition=True, words_per_minute=200, substitutions={}, linkify_fuzzy_links=True, dmath_allow_labels=True, dmath_allow_space=True, dmath_allow_digits=True, dmath_double_inline=False, update_mathjax=True, mathjax_classes='tex2jax_process|mathjax_process|math|output_area', enable_checkboxes=False, suppress_warnings=[], highlight_code_blocks=True)
Tags updated
building [mo]: targets for 0 po files that are out of date
writing output...
building [html]: targets for 1567 source files that are out of date
updating environment: [new config] 1567 added, 0 changed, 0 removed
reading sources... 
(..)
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output...
(..)
copying downloadable files...
copying static files... done
copying extra files... done
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded.

The HTML pages are in _build/html.

[hartmannathan]

Thanks for improving docs!

[hartmannathan]

Looks great. Thank you!