feat(command): select all siblings and children

[dead10ck]

This adds two new related commands:

select_all_siblings

Selects all siblings of the node under the cursor.

select_all_children

Selects all children of the node under the cursor.

select_all_children_in_selection

Selects all children of the node under the cursor, but only if the children are contained inside the starting selection.

[pascalkuthe]

after trying this out for a bit I think select_all_children would benefit a lot from only selecting children that are actually contained in the selection. The current implementation is also useful but i found that quite a lof of nodes have children I don't care about. If someone really wants all children inside the node they can do a-o first. That change would also make the command more predictable I think

[dead10ck]

after trying this out for a bit I think select_all_children would benefit a lot from only selecting children that are actually contained in the selection.

Hmm, but in this case, the command would basically never do anything when the selection is just a cursor, or really any time you don't happen to have an entire node contained in the selection.

But on the other hand, I could see this being useful for if you only want a subset of the children. I'll add a third command that does this.

[dead10ck]

Just added select_all_children_in_selection that only selects if all resulting ranges are contained within the starting selection.

[dead10ck]

Sounds good, will do

[dead10ck]

Ok I've rebased and changed all the motions to use the new in-crate TreeCursor instead of the tree-sitter API directly. This required adding a child iterator in the TreeCursor module.

[dead10ck]

Good suggestions, I took care of them.

[sudormrfbin]

I can finally stop splitting by commas inside a function call to select the arguments :) But it seems the docs weren't updated with the new alt-a and alt-I keybinds.