use `host_permissions` for site origins

[yudukikun5120]

Declaration of site origins in the host_permissions field is preferable.

https://github.com/mkobayashime/manaba-enhanced/blob/47b935a22579dad243f7533cd41cd16f15b96325/src/manifest.ts#L22-L28

I'm afraid to say that we need to upgrade the manifest to v3 since this might work only in manifest v3 or higher.

Refs

• https://developer.chrome.com/docs/extensions/mv3/declare_permissions/
• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/host_permissions