refactor: expose common functions in utils, so users can easily code custom text objects

[stevenxxiu]

Sometimes I want to use text objects that have use cases specific to me.

This exposes common functions used in charwise-textobjs.lua to utils, so users can easily code custom text objects. I think this will make the plugin more useful and flexible.

Checklist

• Used only camelCase variable names.
• If functionality is added or modified, also made respective changes to the
  README.md (the .txt file is auto-generated and does not need to be modified).
• Used conventional commits keywords.

[chrisgrieser]

1. I am somewhat hesitant to expose these functions, since exposing any sort of API carries the implicit promise of keeping them stable. And since they are somewhat main functions I'd probably work on in the feature, making them subject to change. So at the very least, I'd mark it as unstable, so any potential users are aware of this drawback.
2. Also, if this were to be merged, it's not good practice to stuff everything into the utils module, especially if it is only going to be used in one module (the charwise objects) anyway. Moreover, has the bad side effect of creating an unnecessarily huge diff in the commit history.
3. The test is failing, meaning you forgot to run stylua

[stevenxxiu]

1. Sure I can mark them as unstable. How would you like me to do that? Is there some Lua way of doing it?
2. Would you like to keep them in lua/various-textobjs/charwise-textobjs.lua then?
3. I could run StyLua. I just didn't it in this case, since the parts it modified weren't the parts I changed. Would you still like me to run it?

[chrisgrieser]

1. As comment with WARN at the beginning

"Yes" to every question otherwise

[stevenxxiu]

I've addressed your points.

[chrisgrieser]

👍