Add radicale for calendar hosting

[sjamaan]

Thank you for contributing the The Personal Security Checklist 🙌 So that your request can be dealt with quickly, please complete the applicable fields below and the checklist. Thank you :)

Category

Software or Service Addition

Overview

Add link to Radicale, which is an open source CalDAV and CardDAV server that is relatively easy to set up for self-hosting

Supporting Material (if applicable)

GitHub repo

Checklist

Please complete the following checklist

• [ x ] I have performed a self-review (valid markdown formatting, spelling and grammar)
• [ x ] I have indicated whether I have any affiliation with any software/ services added
• [ x ] I agree to follow the repositories code of conduct

[sjamaan]

For future PRs, could you also complete the Association section- just indicate if you're affiliated with the project in anyway. It's just to keep things transparent.

Sure. I just thought if I have no affiliation I could leave it out, and check the box that I filled in the affiliation if applicable. FTR, I'm not affiliated with the project, just a happy user :)