feat: add support for fido yubikeys (#89)

* add support for fido keybind

* add to themes

* fix clang format

* Update ui.c

* docs: add misc stuff about the yubikey

---------

Co-authored-by: javalsai <jvssxxi@gmail.com>

docs/yubikey.md

@@ -0,0 +1,30 @@
+# Yubikeys
+
+Quick reference explaining how yubikeys work for now.
+
+# Enable
+
+Yubikeys are disabled by default, to enable them activate a keybinding for it (`[functions] fido`) in the config file.
+
+Note that pressing this configured keybinding has no difference from trying to log in with an empty password, there's virtually no difference.
+
+`pam_u2f` must be configured with a registered key (`pamu2fcfg`).
+
+# Extra
+
+All my yubikey knowledge comes from the [pr that implemented this](https://github.com/javalsai/lidm/pull/89), please refer to it for extra details. Contributions to this documentation are welcome (explaining more in detail, potential issues... really anything that improves this).
+
+Allegedly this pam module configuration should work:
+
+```pam
+#%PAM-1.0
+
+auth sufficient pam_u2f.so cue
+auth       requisite    pam_nologin.so
+auth       include      system-local-login
+account    include      system-local-login
+session    include      system-local-login
+password   include      system-local-login
+```
+
+Also, I recommend giving the [arch wiki](https://wiki.archlinux.org/title/YubiKey) a read anyways.