add metamask to available extensions

#8671

already added to vault manifest & live on server
brave/vault-updater#43

Auditors:
@bridriver @bsclifton @jonathansampson

js/constants/config.js

@@ -47,6 +47,17 @@ module.exports = {
     authUrl: (userId) => `${vaultHost}/v1/users/${userId}`,
     replacementUrl: adHost
   },
+  // The SHA256 of the SubjectPublicKeyInfo used to sign the extension.
+  // PublicKeySHA256 can be generated by first downloading the CRX with
+  // one of the URLs below.  Then using:
+  // ./script/get-extension-public-key-sha256.py <crx_path>
+
+  // Registers a component which either already exists or not for updates
+  // require('electron').remote.componentUpdater.registerComponent(extensionId) // NOLINT
+  //
+  // Removes any existing extension and performs an install now.
+  // componentUpdater.registerComponent must have been called.
+  // require('electron').remote.componentUpdater.checkNow(extensionId) // NOLINT
   widevineComponentId: 'oimompecagnajdejgnnjijobebaeigek',
   widevineComponentPublicKey: 'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCmhe+02cLPPAViaevk/fzODKUnb/ysaAeD8lpE9pwirV6GYOm+naTo7xPOCh8ujcR6Ryi1nPTq2GTG0CyqdDyOsZ1aRLuMZ5QqX3dJ9jXklS0LqGfosoIpGexfwggbiLvQOo9Q+IWTrAO620KAzYU0U6MV272TJLSmZPUEFY6IGQIDAQAB',
   braveExtensionId: 'mnojpmjdmbbfmejpflffifhffcmidifd',
@@ -73,6 +84,8 @@ module.exports = {
   honeyExtensionPublicKey: 'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC79mayLyuCYY/dyT7Ycr1sVBp9yHrY4mnogVEgu+sDT6+/A121Na+aTw6mFLD6LHgbgHt4fnQ2V/QwcfBSXRTSkGpgNsZAjnYs4/XzZQYKGltWT93EP9zXN1kGbtzfkPGzTakquCfOjbKtbAQKWh8ppzqLhWcRUn9g/PhU99F29QIDAQAB',
   pinterestExtensionId: 'gpdjojdkbbmdfjfahjcgigfpmkopogic',
   pinterestExtensionPublicKey: 'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDB95q2hyt49ZDuVnYI91XaZhqQkbXu0X3fzoNxPxhFbfqGKwtts90LJ7lD5DCIfnBg8WGFhp3eW4GxOglAKrnksmJoyAD5PnSAufx8fD3trZvo/ZAqFx1x5Xm3Rm34EgvVXdralgHSYiqcEU/FX3kYnLLhr2TS4lcrsn1KZd/lcQIDAQAB',
+  metamaskExtensionId: 'nkbihfbeogaeaoehlefnkodbefgpgknn',
+  metamaskPublicKey: 'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAlcgI4VVL4JUvo6hlSgeCZp9mGltZrzFvc2Asqzb1dDGO9baoYOe+QRoh27/YyVXugxni480Q/R147INhBOyQZVMhZOD5pFMVutia9MHMaZhgRXzrK3BHtNSkKLL1c5mhutQNwiLqLtFkMSGvka91LoMEC8WTI0wi4tACnJ5FyFZQYzvtqy5sXo3VS3gzfOBluLKi7BxYcaUJjNrhOIxl1xL2qgK5lDrDOLKcbaurDiwqofVtAFOL5sM3uJ6D8nOO9tG+T7hoobRFN+nxk43PHgCv4poicOv+NMZQEk3da1m/xfuzXV88NcE/YRbRLwAS82m3gsJZKc6mLqm4wZHzBwIDAQAB',
   coinbaseOrigin: 'https://buy.coinbase.com',
   newtab: {
     fallbackImage: {