fix(mappings): Default offset encoding when handling <CR> press

[levouh]

Per here there are a number of functions that now require specifying an offset_encoding. Some examples of other updates to things like nvim-cmp and null-ls.

Looking at all of those functions, this is the only one that I found that gets used in this plugin. As we do not have any attached clients, I do not see this being a huge issue (although I am also pretty naive in terms of the usage and impact) to follow the "norm" and use utf-16 as a default.

[levouh]

Moving to a draft to research & experiment a bit more.

[kristijanhusak]

LGTM. I'm a bit confused why utf-16 instead of utf-8, but since Michael suggested it, I guess that's the right path.

[kristijanhusak]

Thanks!

[mjlbach]

I think the correct fix for you all is using utf-8, utf-16 is only correct if you are applying text edits from a language server. utf-8 assumes the position is encoded with raw bytes, utf-16 assumes code points are encoded with one or two 16-bit code units. This function is very overfit to the protocol.