fix: accept REVISION as env var, specify in instructions

Author: jurevans

apps/extension/FIREFOX_README.md

@@ -46,6 +46,7 @@ yarn wasm:build
 Then, issue the final build command for the Firefox add-on:
 
 ```bash
+export REVISION=487d2a1697f50f06e77677df8e081f868d2a5860
 yarn build:firefox
 ```
 

apps/extension/package.json

@@ -18,8 +18,8 @@
     "build": "yarn wasm:build && yarn clean && yarn build:chrome && yarn build:firefox",
     "build:chrome": "yarn clean:chrome && NODE_ENV=production TARGET=chrome REVISION=$(git rev-parse HEAD) webpack-cli && yarn run web-ext build --s ./build/chrome -a ./build/chrome",
     "build:chrome:beta": "yarn clean:chrome && NODE_ENV=production BETA_RELEASE=true TARGET=chrome REVISION=$(git rev-parse HEAD) webpack-cli && yarn run web-ext build --s ./build/chrome -a ./build/chrome",
-    "build:firefox": "yarn clean:firefox && NODE_ENV=production TARGET=firefox REVISION=$(git rev-parse HEAD) webpack-cli && yarn run web-ext build --s ./build/firefox -a ./build/firefox",
-    "build:firefox:beta": "yarn clean:firefox && NODE_ENV=production BETA_RELEASE=true TARGET=firefox REVISION=$(git rev-parse HEAD) webpack-cli && yarn run web-ext build --s ./build/firefox -a ./build/firefox",
+    "build:firefox": "yarn clean:firefox && NODE_ENV=production TARGET=firefox webpack-cli && yarn run web-ext build --s ./build/firefox -a ./build/firefox",
+    "build:firefox:beta": "yarn clean:firefox && NODE_ENV=production BETA_RELEASE=true TARGET=firefox webpack-cli && yarn run web-ext build --s ./build/firefox -a ./build/firefox",
     "lint": "eslint src --ext .ts,.tsx",
     "lint:fix": "yarn lint -- --fix",
     "lint:ci": "yarn lint --max-warnings 0",