Add a new permission to expose chrome.ipfs API to extensions

[bbondy]

Add a new permission for chrome.ipfs api and notify the user of this permission when they try to install a Chrome extension that has this permission.

Example for an extension that requests the permission "ipfs" we should list that they are requesting it here:

This extension ID is currently published to the chrome store with the ipfs permission for testing:
fpeoodllldobpkbkabpblcfaogecpndd

https://chrome.google.com/webstore/detail/webrecorder-archivewebpag/fpeoodllldobpkbkabpblcfaogecpndd

This is a talk by the same author that would like this API:
https://www.youtube.com/watch?v=evcSETnTBf0

so basically the task is in 2 parts, and 1) is needed before we are allowed to do 2)

1. Show IPFS info in that screenshot above about IPFS
2. Give chrome.ipfs access to any extension that requests it

[stephendonner]

Verified PASSED using the testplan from brave/brave-core#8289

Brave	1.24.47 Chromium: 90.0.4430.41 (Official Build) nightly (x86_64)
Revision	e9c92b1eaca8487e212f3f6bc081fdb6d4863759-refs/branch-heads/4430@{#723}
OS	macOS Version 11.2.3 (Build 20D91)

Steps:

1. Installed extension with ipfs permission in the manifest file, for example https://chrome.google.com/webstore/detail/webrecorder-archivewebpag/fpeoodllldobpkbkabpblcfaogecpndd
2. Confirmed alert about IPFS in permission bubble

3. Went to chrome://inspect#extensions and inspected Webrecorder background page

4. Checked that namespace chrome.ipfs has only 3 public methods available

5. Checked the same for Brave Shield extension, all ipfs methods should be available