add more APIs to api-metadata

[romantaraban]

Adding browser.permissions and browser.privacy.services.passwordSavingEnabled (https://bugzilla.mozilla.org/show_bug.cgi?id=1361364)

[fregante]

It looks like the build failed to start, can you try clicking on Restart build?

What's missing for this one to be merged?

[ExE-Boss]

The permissions API is now present in the api‑metadata.json file, so this should be rebased.

webextension-polyfill/api-metadata.json

Lines 401 to 418 in 2537b23

	"permissions": {
	"contains": {
	"minArgs": 1,
	"maxArgs": 1
	},
	"getAll": {
	"minArgs": 0,
	"maxArgs": 0
	},
	"remove": {
	"minArgs": 1,
	"maxArgs": 1
	},
	"request": {
	"minArgs": 1,
	"maxArgs": 1
	}
	},

[rpl]

Closing this in favor of #133 which is going to add the missing privacy namespace and it also has some additional tests.

(the permissions namespace has been added in #126).