fix(vi-mode)!: add back edit-command-line key binding as 'vv' (#9573)

BREAKING CHANGE: the key binding to open an editor to edit the command line has
been moved from being `v` (press v once) to being `vv` (press v twice). Now, the
action for `v` is the default `visual-mode`, as is in Vim.

Fixes #9573

plugins/vi-mode/vi-mode.plugin.zsh

@@ -64,6 +64,11 @@ zle -N zle-line-finish
 
 bindkey -v
 
+# allow vv to edit the command line (standard behaviour)
+autoload -Uz edit-command-line
+zle -N edit-command-line
+bindkey -M vicmd 'vv' edit-command-line
+
 # allow ctrl-p, ctrl-n for navigate history (standard behaviour)
 bindkey '^P' up-history
 bindkey '^N' down-history