refactor: clean up keybinding implementations

- Cleans and organizes key binding definitions for plugins and user
keybinds.

- Update documentation for keybindings

conf.d/puffer.fish

@@ -0,0 +1,27 @@
+status is-interactive || exit
+
+function _puffer_fish_key_bindings --on-variable fish_key_bindings
+    set -l modes
+    if test "$fish_key_bindings" = fish_default_key_bindings
+        set modes default insert
+    else
+        set modes insert default
+    end
+
+    bind --mode $modes[1] '.' _puffer_fish_expand_dot
+    bind --mode $modes[1] '!' _puffer_fish_expand_bang
+    bind --mode $modes[1] '$' _puffer_fish_expand_buck
+    bind --mode $modes[1] '*' _puffer_fish_expand_star
+    bind --mode $modes[2] --erase '.' '!' '$' '*'
+end
+
+_puffer_fish_key_bindings
+
+set -l uninstall_event puffer_fish_key_bindings_uninstall
+
+function _$uninstall_event --on-event $uninstall_event
+    bind -e '.'
+    bind -e '!'
+    bind -e '$'
+    bind -e '*'
+end