Run CI on pushes and PRs; Fix restore-key (paritytech#70)

* run CI on pushes to master as well as PRs

* fix restore path

https://docs.github.com/en/free-pro-team@latest/actions/guides/caching-dependencies-to-speed-up-workflows#matching-a-cache-key

.github/workflows/release.yml

@@ -1,6 +1,12 @@
 name: Release
 
-on: ['push']
+on:
+  pull_request:
+    branches:
+    - master
+  push:
+    branches:
+    - master
 
 env:
   WASM_BUILD_TOOLCHAIN: nightly-2020-07-20
@@ -67,7 +73,7 @@ jobs:
           node/standalone/target
         key: ${{ runner.OS }}-build-${{ env.WASM_BUILD_TOOLCHAIN }}-${{ hashFiles('**/Cargo.lock') }}
         restore-keys: |
-          ${{ runner.OS }}-build--${{ env.WASM_BUILD_TOOLCHAIN }}
+          ${{ runner.OS }}-build-${{ env.WASM_BUILD_TOOLCHAIN }}
     -
       uses: actions-rs/toolchain@v1
       with: