Merge pull request #276 from Uniswap/fix/ci-sha-pin-github-actions

fix: pin all GitHub Actions to commit SHAs

Author: dgilmanuni

.github/workflows/CI.yml

@@ -16,16 +16,16 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v1
-      - uses: actions/setup-node@v1
+      - uses: actions/checkout@50fbc622fc4ef5163becd7fab6573eac35f8462e # v1
+      - uses: actions/setup-node@f1f314fca9dfce2769ece7d933488f076716723e # v1
         with:
           node-version: ${{ matrix.node }}
 
       - run: npm install -g yarn
 
       - id: yarn-cache
         run: echo "::set-output name=dir::$(yarn cache dir)"
-      - uses: actions/cache@v1
+      - uses: actions/cache@f5ce41475b483ad7581884324a6eca9f48f8dcc7 # v1
         with:
           path: ${{ steps.yarn-cache.outputs.dir }}
           key: ${{ matrix.os }}-yarn-${{ hashFiles('**/yarn.lock') }}