Added support for a unique id when caching the site's manifest.

[barbhackk]

Hi,

When used with a PWA which generates different content for each page (for example a profile page with a firstname, a lastname and an avatar and therefore different icons and splash screens) it happens that between several tabs open at the same time, the icons generated are identical at first (as long as you don't close the tabs - grants the documentation).

Indeed, the manifest file as well as the icons are stored with an identifier __pwacompat_manifest or __pwacompat_ios

To avoid this, I added support for a unique ID for each key.

If you need to display a PWA whose icons are dynamic, please enter a meta pwacompat-manifest-id tag with a unique identifier like uuid for exemple.

<meta name="pwacompat-manifest-id" content="1124d9e8-6266-4bcf-8035-37a02ba75c69" />

Otherwise you will always have the same information between all tabs even if the content is different.
Thus the key in session will be personalized with the identifier.

Thanks ☺️,

Sebastien

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