Use generics for rows and columns

[JomerDev]

This PR removes the rows setting and instead uses generics for rows and columns.
This allows for asserts in some places to make sure the users aren't passing in values larger than the set rows or columns values.
With this support for screens up to 20x4 was added (I know the name of the library specifies 1602 but I don't think there is a point in not supporting them, it only cost some very small changes)

(I'm also currently preparing a PR to support the creating of new characters which the LCDs allow as well)

[KuabeM]

Nice, thanks! I'll review it in the upcoming days :)

Would you mind adding a comment to the readme that other 'formats' are also supported? I assume you tested this with some hardware, so you could even add a link/reference to it.

Also, looking forward to the custom character PR!

[JomerDev]

Done. The formatting is also fixed

I'll open the custom character PR after this one is merged, I made the mistake of basing it on these changes

[KuabeM]

Reviewed the code, looks good to me :) I don't have anything at hand to test it.

Where you able to test it with all the different supported sizes?

[JomerDev]

I tested it with a 20x4 LCD, the others I haven't checked. But the specific changes came again from the C++ library I mentioned before, so anything they support should work here now as well

[KuabeM]

Actually, there is a simple way! You just need to wrap the assert! in a const block. They are supported since rust 1.79.0, see the rustc PR

        const { assert!(COLUMNS > 0, "COLUMNS needs to be larger than zero!") };

The error messages are not super nice, but better then a runtime fail.

Could you add these consts?

[JomerDev]

Done. I could have sworn I tried that, but I think I didn't add the brackets around the assert.
The asserts in set_cursor can't be const since the arguments to the function aren't const

[KuabeM]

Thanks again, looking forward to the custom char PR :)