add github actions

.github/actions/cache-bootstrap/action.yml

@@ -0,0 +1,31 @@
+name: cache-bootstrap
+description: Creates a cache with the given extension for lerna packages
+inputs:
+  extension:
+    description: Extension for cache name
+  partial:
+    description: Boolean flag to describe whether or not to run a partial bootstrap when finding cache
+    default: false
+runs:
+  using: composite
+  steps:
+    # for always overriding cache, use: pat-s/always-upload-cache@v2.1.5
+    - uses: actions/cache@v2
+      id: cache
+      with:
+        path: |
+          node_modules
+          */*/node_modules
+        key: ${{ runner.os }}-yarn-${{inputs.extension}}-v5-${{ hashFiles('**/yarn.lock') }}
+      # We want to only bootstrap and install if no cache is found.
+      # Futhermore, we might want to do a partial, hoisted, bootstrap towards
+      # the base branch if it exists, otherwise we choose develop for this.
+    - run: |
+        if [[ "${{steps.cache.outputs.cache-hit}}" != "true" ]]; then
+          yarn install --frozen-lockfile
+          yarn bootstrap --concurrency=2
+        elif [[ "${{inputs.partial}}" = "true" ]]; then
+          [[ ! -z "${GITHUB_BASE_REF}" ]] && ref="${GITHUB_BASE_REF#refs/heads/}" || ref="develop"
+          yarn bootstrap --npm-client=npm --hoist --since "origin/${ref}...HEAD" --concurrency=2 
+        fi
+      shell: bash