docs: update readme.

[BenjaminMummery]

Problem Statement

Updates the readme to include instructions for americanise inline ignores.

Checklist

• The PR title follows semantic release rules (starts with one of build, chore, ci, docs, feat,fix, perf, style, refactor, test). Note that this is CASE SENSITIVE!
• All commits in this PR follow semantic release rules.

[github-actions]

✅ Result of Pytest Coverage

_______________ coverage: platform linux, python 3.11.13-final-0 _______________

Name	Stmts	Miss	Cover
Name	Stmts	Miss	Cover
src/_shared/comment_mapping.py	17	0	100%
src/_shared/config_parsing.py	42	0	100%
src/_shared/copyright_parsing.py	76	2	97%
src/_shared/exceptions.py	4	0	100%
src/_shared/print_diff.py	22	0	100%
src/_shared/resolvers.py	9	0	100%
src/add_copyright_hook/add_copyright.py	171	4	98%
src/add_msg_issue_hook/add_msg_issue.py	67	0	100%
src/americanise_hook/americanise.py	80	1	99%
src/no_import_testtools_in_src_hook/no_import_testtools_in_src.py	46	0	100%
src/sort_file_contents_hook/sort_file_contents.py	102	0	100%
src/update_copyright_hook/update_copyright.py	36	0	100%
TOTAL	672	7	99%

~ 867 passed in 18.90s ~