Added Mastodon link to navigation drawer (bitfireAT/davx5#179)

* Added mastodon icon

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>

* Added mastodon link to drawer

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>

* Added mastodon link action

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>

* Mastodon icon tint

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>

* Added Mastodon icon to main

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>

Signed-off-by: Arnau Mora <arnyminer.z@gmail.com>