Add new 'chrome-extension' PURL type to Registered PURL Types

[mjherzog]

We expect to merge the PR for the new 'chrome-extension' soon. See

• Add new PURL type: 'chrome-extension' purl-spec#522

I updated the PR to ask the contributor about an icon for the website

[johnmhoran]

@mjherzog So nothing to do until we get the icon? Or add the type to the grid now?

[mjherzog]

Good question. Let's wait until tomorrow to see if we get an icon.

[mjherzog]

From package-url/purl-spec#522 we have the suggestion of:

I checked: https://developer.chrome.com/docs/webstore/branding and guidelines for an extension - which says to use an icon like (small size).

Not sure whether we have room for the icon plus the block text but this indicates that we would at least want to use the "truncated" version of the base Google Chrome icon to distinguish the extensions from Chrome itselfl