Properly parse all allowed iTunes RSS explicit field values

[valeriecodes]

Per the iTunes spec: https://help.apple.com/itc/podcasts_connect/#/itcb54353390

If you specify yes, explicit, or true, indicating the presence of explicit content, the iTunes Store displays an Explicit parental advisory graphic for your podcast.

If you specify clean, no, or false, indicating that none of your podcast episodes contain explicit language or adult content, the iTunes Store displays a Clean parental advisory graphic for your podcast.

Currently the parser only handles the values of true or yes for explicit and false or clean for clean.

[kou]

Ah, sorry. I missed this.
I fixed this with other implementation. The spec says yes, explicit, true, clean, no and false are valid values but your change supports only explicit, yes, clean and no.

Thanks for your report. I didn't notice it when I added <itunes:> support.