Add Arabic abjad numerals

[seloumi]

Arabic abjad numeral for alphabetic numbering #168.

[MDLC01]

How to fix the issues raised by CI. You can click on the "Commit suggestion" button on each of them.

[MDLC01]

Thanks for addressing the CI issues.

Regarding the actual content, I am not fully confident I understand how abjad numerals work. According to the Wiktionary page you linked,¹ this wouldn't be a positional system nor a bijective system, but an additive system, similar to Roman numerals, where each symbol has a value, and concatenated symbols signify addition of their respective values.

This boils down to the following question: if you had eleven headings using this numbering, how would you expect them to be numbered?

Option A (currently implemented in this PR)	Option B (what I understand from the Wiktionary page)
أ ب ج د ه و ز ح ط ي ك	أ ب ج د ه و ز ح ط ي يأ

Finally, I have a question regarding the way the fifth number should be displayed. Should it be "ه" or "ه‍"?

Footnotes

1. https://en.wiktionary.org/wiki/Appendix:Abjad_numerals ↩

[seloumi]

Arabic alphabetic abjad numbering is like Latin alphabetic numbering: a,b,c,........
The correct result of numbering should be like option A (like what we did in this PR).
For the fifth letter it should be like this "ه‍".

[seloumi]

Why do these errors reappear every time? I only changed the fifth character, and the errors popped up again!

[MDLC01]

Then do you know what the Wiktionary page is referring to and whether it would make sense to implement that as well (in a separate PR)?

Regarding the fifth letter, this will require some change to the infrastructure. I opened a separate PR for that: #171.

Why do these errors reappear every time? I only changed the fifth character, and the errors popped up again!

In this case, this is due to the aforementioned infrastructure limitation. But more generally, even the slightest change to a numeral system will cause its magic number to change, so the corresponding test will fail. The goal is that we check that everything works as intended once, and then write the magic number. If something breaks in the future, we will notice it because the magic number will change.

[seloumi]

What matters to us is the alphabet numbering, the content of the link describes an old method for converting letters and words into numbers ("حساب الجمل").