Update workflow

Author: jpmckinney

.github/workflows/ci.yml renamed to .github/workflows/lint.yml

@@ -1,4 +1,4 @@
-name: CI
+name: Lint
 on: [push, pull_request]
 env:
   BASEDIR: https://raw.githubusercontent.com/open-contracting/standard-maintenance-scripts/master
@@ -10,5 +10,11 @@ jobs:
     - uses: actions/setup-python@v1
       with:
         python-version: 3.6
+    - uses: actions/cache@v1
+      with:
+        path: ~/.cache/pip
+        key: ${{ runner.os }}-pip-${{ hashFiles('.github/workflows/lint.yml') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-
     - run: curl -s -S --retry 3 $BASEDIR/tests/install.sh | bash -
     - run: curl -s -S --retry 3 $BASEDIR/tests/script.sh | bash -