build(ci): replace third-party shellcheck action (openlawteam#209)

* replace third-party shellcheck action and use checkout@v2

* specify files to check

* name lint js job

.github/workflows/lint.yml

@@ -3,28 +3,30 @@ name: Linters on push
 
 jobs:
   lint-js:
+    name: Run JS lints
     runs-on: ubuntu-latest
     steps:
       - uses: actions/setup-node@v1
         with:
           node-version: "10.x"
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - run: npm ci
       - run: npm run lint
       - run: npm run style
 
   lint-shell:
-    runs-on: ubuntu-latest
+    name: Run shellcheck
+    runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v1
-      - name: Shellcheck Lint
-        uses: azohra/[email protected]
+      - uses: actions/checkout@v2
+      - name: shellcheck
+        run: shellcheck ci/*.sh scripts/*.sh
 
   lint-scala:
     name: Run scalafmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
         with:
           fetch-depth: 1
       - uses: openlawteam/scalafmt-ci@v2