- Changed MSRV to v1.65.
  Discussed this with @dani-garcia, and we will support **N-2**.
  This is/will be the same as for the `time` crate we use.
  Also updated the wiki regarding this https://github.com/dani-garcia/vaultwarden/wiki/Building-binary
- Removed backtrace crate in favor of `std::backtrace` stable since v1.65
- Updated Rust to v1.67.1
- Updated all the crates
- Updated the GHA action versions
- Adjusted the GHA MSRV build to extract the MSRV from `Cargo.toml`

This commit prepares Vaultwarden for the Re-Licensing to AGPLv3
Solves #2450

master branch has been renamed to main.

master branch has been renamed to main.

master branch has been renamed to main.

master branch has been renamed to main.

Fixed 'Bitwarden clients' link, it should lead to https://bitwarden.com/download/ and not to https://bitwarden.com/#download/

The link is already pointing to the new image location, but the badge
source was somewhat confusingly showing stats for the old image.

Just some basic grammar updates in the "get in touch" section.