Set checkbox to specific state

[e-mar404]

set_checkbox to specific state

Can be called as command :Obsidian set_checkbox [STATE] with the state being an optional param.

There will be a validation check to make sure that the passed state is part of the checkbox order since if it isn't this would cause issues with the auto cycling of toggle_checkbox.

This would be implementing issue #316.

Note: Did not add tests since they would break due to the treesitter issue that also affects toggle_checkbox, as mentioned on #300.

[neo451]

@e-mar404

great PR!

Some ideas:

1. no need to worry about tests for now.
2. I was more imagining that the vim.fn.getchar logic to be in the API function, so that like smart_action and nav_link, we can provide a default map or an instruction to a simple map.
3. As I discussed in that issue, I don't think using a user command to set it to a specific state is economical, and I don't want to make the already crowed namespace have more members. So maybe just stick to the function approach.

Also users can easily register their own command now, https://github.com/obsidian-nvim/obsidian.nvim/wiki/Extensions

[e-mar404]

@neo451 Thanks!

I removed the user command and just kept the logic to be encapsulated on the api function.

For documentation I am not sure where to write about it's existence. It doesn't feel like something that should have a default key map since this can have more of a subjective mapping. I was thinking of adding it to the keymaps section of the README and docs but just mentioning that it does not have a default keymap and that is something that is user defined instead.

What do you think of that approach instead?