Add support for multiple evil-escape-key-sequences

[al3xandru]

This is just a minor request: as a vimmer using jk as an escape sequence, it would be very helpful to allow defining multiple evil-escape-key-sequences that would ease the transition to the Spacemacs's default fd.

Changing the evil-escape-key-sequence was one of the first things I've learned and done after starting Spacemacs. As I leaned more into Spacemacs spc prefix combined with spc f s I felt tempted to give a 2nd chance to fd. As a newbie, going the key-chord route sounds a bit scary/too complicated (maybe because what I have read was not very conclusive)

_Note: originally reported syl20bnr/spacemacs#5445 and with a workaround based on key-chord.

[yzhuang]

Another vote for this.
My use case is that I tend to use both jk and kj for entering normal mode, so it would be nice if this feature is added.

[syl20bnr]

For jk and kj use case check the configuration variables, there is one to set the sequence as unordered.

[yzhuang]

That worked for me. Thanks!

[elvis-sik]

I would need this to bind both fd and FD (for when I am typing with caps on).