[discovery] Added foodnetwork and hgtv (fixes #17947)

[VietTPham]

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Description of your pull request and other information

foodnetwork and hgtv updated their site to use the discovery format of listing content. fixes #17947

[tv21]

I manually added this patch and it does work on hgtv at least. Thank you!

[dnlzzxz]

I manually added this patch and it does work on hgtv at least. Thank you!

Hey, how can I learn to manually add a patch? thanks in advance. @tv21

[nerdily]

I manually added this patch and it does work on hgtv at least. Thank you!

Hey, how can I learn to manually add a patch? thanks in advance. @tv21

I'd love to know too! If this is working for HGTV, I'd like to test it. I have a login for it and everything.