Support for Proton Drive

### Please agree to the following

- [x] I have searched [existing issues](https://github.com/cryptomator/android/issues?q=) for duplicates
- [x] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/android/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

Adding support for Proton Drive cloud service

### Motivation

Although being advertised as privacy-friendly and end-to-end encrypted, such popular cloud service as Proton Drive should be added to supported cloud services in Cryptomator. Even open source code could have some flaws or issues, so adding extra layer of protection should be possible for those, who are interested in such solution.

### Considered Alternatives

_No response_

### Anything else?

_No response_