Fix grammar in the README

[ErikPohl444]

Fixed some grammar in the readme. Closes #483

[MarshalX]

Thank you! Could you please review the entire README and fix the English? Also, I want to mention, we have 2 copies of the readme. One for GitHub and another one for the docs website. You should update this file as well: https://github.com/MarshalX/atproto/blob/main/docs/source/readme.content.md

[ErikPohl444]

Hello! Glad to help. I'll first align my current changes into:
https://github.com/MarshalX/atproto/blob/main/docs/source/readme.content.md

Then I'll read and revise as needed, submitting changes across both.

BTW: This is an excellent README overall, and one which got me started quickly. The descriptive nature and word-choices are great. I'd be honored to contribute little edits here and there when recommended.

Thank you.

[ErikPohl444]

Reviewed and synched changes between readmes.

[MarshalX]

@ErikPohl444 thank you! I synced changes between readmes in the single Pull Request. Pls check. All good?

[ErikPohl444]

All good. Thank you!