Update hosting_providers.json

[BuildingTech24]

Added Proton Mail to list of hosting providers.

Pull Request Checklist

• I have carefully read and fully understood the instructions in the README file, and I attest that this pull request conforms to those instructions.
  • I have placed a link in exactly one of {tutorial, announcement, plan}
  • If the user must take any additional action to add a certificate, I have set the category to partial
  • The note field is not a generic description of the offerings; it notes the language, or which products have full support in an otherwise partial provider. Otherwise, it is empty.