Add ctrl-r, ctrl-a and ctrl-e support in vi-mode (#4994)

* Add ctrl-r support in vi-mode to perform backward search in history
* Add ctrl-a support to move to bol in vi-mode
* Add ctrl-e support to move to eol in vi-mode
Signed-off-by: NDouglas Drumond <douglas@cafelinear.com>

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

@@ -28,6 +28,13 @@ bindkey '^?' backward-delete-char
 bindkey '^h' backward-delete-char
 bindkey '^w' backward-kill-word
 
+# allow ctrl-r to perform backward search in history
+bindkey '^r' history-incremental-search-backward
+
+# allow ctrl-a and ctrl-e to move to beginning/end of line
+bindkey '^a' beginning-of-line
+bindkey '^e' end-of-line
+
 # if mode indicator wasn't setup by theme, define default
 if [[ "$MODE_INDICATOR" == "" ]]; then
   MODE_INDICATOR="%{$fg_bold[red]%}<%{$fg[red]%}<<%{$reset_color%}"