chore: update github actions configuration (#753)

This PR was generated using Autosynth. 🌈


<details><summary>Log from Synthtool</summary>

```
2020-03-22 04:09:21,101 synthtool > Executing /tmpfs/src/git/autosynth/working_repo/synth.py.
.eslintignore
.eslintrc.yml
.github/ISSUE_TEMPLATE/bug_report.md
.github/ISSUE_TEMPLATE/feature_request.md
.github/ISSUE_TEMPLATE/support_request.md
.github/PULL_REQUEST_TEMPLATE.md
.github/publish.yml
.github/release-please.yml
.github/workflows/ci.yaml
.kokoro/common.cfg
.kokoro/continuous/node10/common.cfg
.kokoro/continuous/node10/docs.cfg
.kokoro/continuous/node10/lint.cfg
.kokoro/continuous/node10/samples-test.cfg
.kokoro/continuous/node10/system-test.cfg
.kokoro/continuous/node10/test.cfg
.kokoro/continuous/node12/common.cfg
.kokoro/continuous/node12/test.cfg
.kokoro/continuous/node8/common.cfg
.kokoro/continuous/node8/test.cfg
.kokoro/docs.sh
.kokoro/lint.sh
.kokoro/presubmit/node10/common.cfg
.kokoro/presubmit/node10/docs.cfg
.kokoro/presubmit/node10/lint.cfg
.kokoro/presubmit/node10/samples-test.cfg
.kokoro/presubmit/node10/system-test.cfg
.kokoro/presubmit/node10/test.cfg
.kokoro/presubmit/node12/common.cfg
.kokoro/presubmit/node12/test.cfg
.kokoro/presubmit/node8/common.cfg
.kokoro/presubmit/node8/test.cfg
.kokoro/presubmit/windows/common.cfg
.kokoro/presubmit/windows/test.cfg
.kokoro/publish.sh
.kokoro/release/docs.cfg
.kokoro/release/docs.sh
.kokoro/release/publish.cfg
.kokoro/samples-test.sh
.kokoro/system-test.sh
.kokoro/test.bat
.kokoro/test.sh
.kokoro/trampoline.sh
.mocharc.js
.nycrc
.prettierignore
.prettierrc
CODE_OF_CONDUCT.md
CONTRIBUTING.md
LICENSE
README.md
codecov.yaml
renovate.json
samples/README.md
2020-03-22 04:09:21,888 synthtool > Wrote metadata to synth.metadata.

```
</details>

.github/workflows/ci.yaml

@@ -9,9 +9,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [10, 12, 13]
+        node: [8, 10, 12, 13]
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: ${{ matrix.node }}
@@ -30,7 +30,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: 12
@@ -39,7 +39,7 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: 12
@@ -48,7 +48,7 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: 13