Added picture links and links completion

[ASMfreaK]

Hello! Thanks for the nice repo!
Here is a new extension for the wiki!

[TeddyDD]

Hi! Thanks for your contribution. I need to reviews your changes carefully since they add quite a lot of complexity. I noticed some issues:

• wiki command does not show completion

• after image expansion with @ tag you can't go to new line with enter, you have to exit inset mode and enter it again

• not sure if @+ syntax is good idea. Maybe ! should be modifier and user would create pages in the old way? WDYT?

[TeddyDD]

review

[TeddyDD]

is separate hook necessary?

[TeddyDD]

remove this echo, no need to be verbose

[ASMfreaK]

I'll reiterate on this. I'm sorry. I've posted it half asleep, so it is very messy. I've spotted a very disappointing typo in README.md too.

[TeddyDD]

no worries, I have typos all over the place :) I really like idea of image links and completion, and it works quite well. Actually only thing I don't like is + sign required for creating pages, but it shoudn't be too hard to change.

[TeddyDD]

I'm integrating some features from this pr in https://github.com/TeddyDD/kakoune-wiki/tree/update-07 branch:

• expand picture command
• @!image syntax
• completion

[TeddyDD]

I'm rewriting this plugin from scratch. Closing this PR since it won't apply to new version.