support shortcuts in surround command

[TeddyDD]

some commands supports q Q b g shortcuts, It would be nice to add them to surround command as well

[h-youhei]

I thought it would be useful to surround with pressed char when I implemented surround command.
So I haven't supported q Q b B a g shortcuts intentionally.
But I have used the feature for symbols only.
I'll add q Q b B a g shortcuts for surround command.

[h-youhei]

for change surround

[TeddyDD]

Thanks :)