Add new 'grapheme_indices' function

[alexdowad]

This new function allows luautf8 to be used for Unicode grapheme segmentation. Discussion is in #46.

Thanks to @Erutuon for suggesting the API for the new function.

I think I've covered all my bases; documentation, adding tests, etc.

[alexdowad]

Just added another test case to test.lua.

[starwing]

@alexdowad is there any questions for comments?

[alexdowad]

@alexdowad is there any questions for comments?

I believe I'm done on this one, unless you notice anything when reviewing which needs to be improved.

[starwing]

@alexdowad there are two comments in code, you could see whether they need fixed.

[alexdowad]

@alexdowad there are two comments in code, you could see whether they need fixed.

OK, I'm sorry, @starwing, I didn't understand what you meant in your previous post.

Will look at your comments. Thanks very much.

[alexdowad]

@starwing, I can't find your comments. Could you please share them again?

[starwing]

@alexdowad here:

[alexdowad]

Thanks so much, just looking into those good comments...

[alexdowad]

I have amended the code to use byte_relat and to throw errors on invalid values of the start and end arguments.

[alexdowad]

@starwing Your comment about the code which handles sequences of Indic "extend", "linker", and "consonant" codepoints is also very correct. I have amended the code accordingly.

[starwing]

Thanks for contributing! Merged 👍