feat: add linewise deletion of surrounds

[phgz]

Skeleton implementation for #305.

Mainly missing doc and tests.

[kylechui]

One minor concern that I have is how cS will now be interpreted, i.e. does the "line" for S mean that the replacement will be on new lines (as is current), or that it will delete the lines the surround is on (as you propose)? I feel that this might not be the most intuitive.

[phgz]

I see. Well personally I do not directly use dS, but rather dVs (remap) as mentioned in #305. So maybe it could directly be added as such, although I'm not sure how many people are familiar with the force-motion feature.

[kylechui]

Hmm... I'm personally quite wary of adding new features nowadays; I would probably like to see a few more people say that they really want this feature before I commit to adding it in. I personally don't think most people know about force-motion; many don't even know about motion or text-object 😉

[phgz]

No problem! I'll maintain my fork hehe.