Accept first word with Ctrl-B

[m18coppola]

Added functionality to insert first word of suggestion.
I decided on using Ctrl-B for the default key bind, as it's one of the few unused insert-mode commands that also isn't used for terminal control flow.

I used ^\s*\S\+ as the pattern to match the first word in the suggestion. I experimented with alternative patterns that matched against \w's or matched up until a word boundary, but found that it was annoying, especially around sections of code that was symbol dense, i.e. for (i = 0; i < x; i++) {. I may come back with a better pattern in the future.

Resolves #2

[ggerganov]

Looking good.

Btw, it would be really good if we figure out how to not send a new completion request and instead to keep the remaining of the suggestion. This would also be needed when you start typing the same characters from the suggestion - no need to send new requests. But even as it is, it's a good improvement.

[m18coppola]

It's currently got a bug where if you try to accept a word on a completion that doesn't start at the end of line, it will delete your code:

I'm working on that right now. I really like the idea of keeping the remaining completion instead of doing a new curl request.

[m18coppola]

I fixed the bug where llama#accept_fim('word') was deleting text that came after the cursor.
I began investigating how to prevent making a new request when accepting only a word but found a catch. My first instinct was to make sure that llama#fim_cancel() was not called when accepting a word, but the CursorMoved event handler calls llama#fim_cancel() whenever the cursor moves, including when the cursor shifts while accepting a suggestion. I believe this change will be a little more involved and should be in a PR of its own, or perhaps be included with the PR that resolves #3