next.js

586ae4e8 - Support Two-letter Language Codes(ISO-639-1) to metadata HrefLang types (#46285

Support Two-letter Language Codes(ISO-639-1) to metadata HrefLang types (#46285 As written in the [reference link](https://hreflang.org/what-is-a-valid-hreflang) in `alternative-urls-types.ts`, two-letter language codes in ISO 639-1 format can also be used as HrefLang. So, adding Two-letter language codes into `HrefLang` type in `alternative-urls-types.ts`. closes #46284