feat(default): bind 'SPC b y' to yank whole buffer

Evil may not always be available in all buffers, and in line with the
filepath yank commands on SPC f y/Y, I thought this command could be
useful. However, I omitted a "replace buffer with paste" command because
in any editing context, evil should be available, in which case it'd be
redundant with `vigp` (or yig for yanking the buffer).

Close: #5281
Co-authored-by: Alex Palaistras <deuill@users.noreply.github.com>

modules/config/default/autoload/text.el

@@ -32,6 +32,12 @@
          ((fboundp 'helm-show-kill-ring) #'helm-show-kill-ring)
          ((error "No kill-ring search backend available. Enable ivy, helm or vertico!")))))
 
+;;;###autoload
+(defun +default/yank-buffer-contents ()
+  "Copy entire buffer into kill ring."
+  (interactive)
+  (clipboard-kill-ring-save (point-min) (point-max)))
+
 ;;;###autoload
 (defun +default/yank-buffer-path (&optional root)
   "Copy the current buffer's path to the kill ring."