Add a section on typo fixes and large PRs

[willingc]

Describe the enhancement or feature you would like

This came out of a discussion on Discord https://discord.com/channels/854719841091715092/867922302996734073/1296024336490037269 and recent PRs that typo fix the whole codebase.

The goal of this section is:

• to clarify which directories in the CPython repo are suitable for typo fixes. (Docs, Internal Docs, and sometimes News)
• encourage smaller reviewable PRs (good practice, easier for maintainers to review)
• remind that large PRs unnecessarily notify large numbers of reviewers (respect for the time of others)
• mention that large PRs with typo fixes in other directories will be closed and guidance to this section to be followed
• set up contributors for future success and for tackling more timely issues/documentation

Describe alternatives you have considered

No response

Additional context

No response