Add a spell and grammar checker in GitHub actions

[nmenon]

In addition, please add a spelling and grammar checker.
Example:
https://blog.alta3.com/topics/scm-and-pipelines/adding-spell-checking-as-a-github-action/ or the equivalent.

While at it request adding it to build check flow and contribute guide

[StaticRocket]

Without a tuned wordlist enchant with https://github.com/sphinx-contrib/spelling reports about 6589 errors just for OS=linux DEVFAMILY=AM62X . This ignores grammar and contextual information, often tagging directories, build options and other parameters incorrectly.

I'm debating about trying to get something more advanced like merging languagetool so it's more context aware, but even that will have a lot of false positives. Not sure this is something we want to add right now.

[cshilwant]

@StaticRocket Probably we can add it just for commit message?
Though I'm anticipating false alarms there as well

[StaticRocket]

This is a can of worms I'm not prepared to open right now. I'm personally prioritizing cicd builds and rstcheck fixes first.