fix: restore Android support (#770)

This change:
- removes 'incognito' key from Firefox manifest
- unifies manifest for Firefox on Desktop and Android
  (bundle:fennec calls bundle:firefox)
  making it possible to publish a single package supporting both
  platforms to work around AMO issues described in:
  #761 (comment)
- adds `manifest.chromium.json` for Chrome-specific keys

add-on/manifest.chromium.json

@@ -0,0 +1,3 @@
+{
+  "incognito": "not_allowed"
+}

add-on/manifest.common.json

@@ -58,6 +58,5 @@
     }
   ],
   "content_security_policy": "script-src 'self'; object-src 'self'; frame-src 'self';",
-  "default_locale": "en",
-  "incognito": "not_allowed"
+  "default_locale": "en"
 }

package.json

@@ -26,18 +26,18 @@
     "build:js": "run-s build:js:*",
     "build:js:webpack": "webpack -p",
     "build:minimize-dist": "shx rm -rf add-on/dist/lib add-on/dist/contentScripts/ add-on/dist/bundles/ipfsProxyContentScriptPayload.bundle.js",
-    "build:bundle-all": "cross-env RELEASE_CHANNEL=${RELEASE_CHANNEL:=dev} run-s bundle:chromium bundle:brave:$RELEASE_CHANNEL bundle:fennec:$RELEASE_CHANNEL bundle:firefox:$RELEASE_CHANNEL",
+    "build:bundle-all": "cross-env RELEASE_CHANNEL=${RELEASE_CHANNEL:=dev} run-s bundle:chromium bundle:brave:$RELEASE_CHANNEL bundle:firefox:$RELEASE_CHANNEL",
     "build:rename-artifacts": "./scripts/rename-artifacts.js",
     "bundle": "run-s bundle:*",
-    "bundle:chromium": "shx cp add-on/manifest.common.json add-on/manifest.json && web-ext build -a build/chromium && run-s build:rename-artifacts",
+    "bundle:chromium": "shx cat add-on/manifest.common.json add-on/manifest.chromium.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/chromium && run-s build:rename-artifacts",
     "bundle:firefox": "shx cat add-on/manifest.common.json add-on/manifest.firefox.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/firefox/  && run-s build:rename-artifacts",
     "bundle:firefox:dev": "npm run bundle:firefox",
     "bundle:firefox:stable": "npm run bundle:firefox",
     "bundle:firefox:beta": "shx cat add-on/manifest.common.json add-on/manifest.firefox.json add-on/manifest.firefox-beta.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/firefox/  && run-s build:rename-artifacts",
-    "bundle:fennec": "shx cat add-on/manifest.common.json add-on/manifest.firefox.json add-on/manifest.fennec.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/fennec/  && run-s build:rename-artifacts",
-    "bundle:fennec:dev": "npm run bundle:fennec",
-    "bundle:fennec:stable": "npm run bundle:fennec",
-    "bundle:fennec:beta": "shx cat add-on/manifest.common.json add-on/manifest.firefox.json add-on/manifest.firefox-beta.json add-on/manifest.fennec.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/fennec/  && run-s build:rename-artifacts",
+    "bundle:fennec": "npm run bundle:firefox",
+    "bundle:fennec:dev": "npm run bundle:firefox:dev",
+    "bundle:fennec:stable": "npm run bundle:firefox:stable",
+    "bundle:fennec:beta": "npm run bundle:firefox:beta",
     "bundle:brave": "shx cat add-on/manifest.common.json add-on/manifest.brave.json | json --deep-merge > add-on/manifest.json && web-ext build -a build/brave/  && run-s build:rename-artifacts",
     "bundle:brave:dev": "npm run bundle:brave",
     "bundle:brave:stable": "npm run bundle:brave",