Clarify ASCII numerals in alpha_dash and alpha_num validation rules

[austincarpenter]

ASCII characters in the \p{L} regex ranges are clarified as a-z and A-Z for the alpha_dash and alpha_num validation rules. ASCII numerals in the \p{N} range (0-9) are not.

[austincarpenter]

Should the alpha_dash description go one step further? I.e.:

"To restrict this validation rule to characters in the ASCII range (a-z, A-Z, 0-9, - and _), you may provide..."

I feel like most people would always opt for the :ascii variant of the rule and having the ranges comma-separated like this without describing them makes visually identifying the rules much easier.

[shaedrich]

Maybe, we could highlight the "numeric" as alpha_dash looks like the alpha rule plus an additional dash, not the alpha_num rule plus dash:

Suggested change

The field under validation must be entirely Unicode alpha-numeric characters contained in [`\p{L}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AL%3A%5D&g=&i=), [`\p{M}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AM%3A%5D&g=&i=), [`\p{N}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AN%3A%5D&g=&i=), as well as ASCII dashes (`-`) and ASCII underscores (`_`).

The field under validation must be entirely Unicode alpha-**numeric** characters contained in [`\p{L}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AL%3A%5D&g=&i=), [`\p{M}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AM%3A%5D&g=&i=), [`\p{N}`](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5B%3AN%3A%5D&g=&i=), as well as ASCII dashes (`-`) and ASCII underscores (`_`).