Add Saudi riyal currency symbol

[MDLC01]

This PR adds the symbol for the Saudi riyal currency, which was added to Unicode in version 17.0.0.

I chose the name riyal instead of something more specific because this is the only riyal in active use.¹

Footnotes

1. According to @Enivex on Discord: https://discord.com/channels/1054443721975922748/1277628305142452306/1431770363737407562 ↩

[Enivex]

I should say. There are multiple currencies called riyal/rial, but to my knowledge the alternative U+FDFC ﷼ is not in active use for any of them.

Edit:

https://www.unicode.org/L2/L2025/25076-sew-recommendations-saudi-riyal.pdf

U+FDFC RIAL SIGN was encoded in Unicode 3.2 as a compatibility character for Iranian standards that defined such
a character

[Enivex]

This presumably also needs the update to Harfrust