Update README.md

[demilolu]

• Update link to Join Community Badge
• Add "Celebrate Hacktoberfest" badge linking to our handbook to guide new users as to how to interact with our projects in Hacktoberfest

Contributes to # (add issue number here. i.e. #302)

What did you do?

Updated the badges in our read.me as such. Adding "Celebrate Hacktoberfest"

Why did you do it?

So that contributors want to contribute in Hacktoberfest know exactly what to do and also have a clear path into our Slack community so we can grow our community

How have you tested it?

I have tested this in other repos and it has worked: see https://github.com/Call-for-Code-for-Racial-Justice/Legit-Info#readme

Were docs updated if needed?

• [ ] No
• [x] Yes
• [ ] N/A

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] documentation update only

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes generate no new console logs
• [ ] Fixes entire issue
• [ ] Partial fix for issue

[Sabine-Justilien]

@demilolu Based on Gerald's feedback, do you intend on adding the general slack channel to all of OS projects versus their respective channels like https://callforcode.slack.com/archives/C01CDLTU015 #racial-justice-five-fifths-voter or https://callforcode.slack.com/archives/C01D7MS0G0K #racial-justice-general?