Add a complication check GHA

It's based on Eldev.

.github/workflows/test-emacs.yml

@@ -0,0 +1,34 @@
+name: Test Emacs
+
+on:
+  push:
+    paths: ['**.el']
+  pull_request:
+    paths: ['**.el']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    continue-on-error: ${{matrix.emacs_version == 'snapshot'}}
+
+    strategy:
+      matrix:
+        emacs_version: ['26.3', '27.1', '28.1', 'snapshot']
+
+    steps:
+    - name: Set up Emacs
+      uses: purcell/setup-emacs@master
+      with:
+        version: ${{matrix.emacs_version}}
+
+    - name: Install Eldev
+      run: curl -fsSL https://raw.github.com/doublep/eldev/master/webinstall/github-eldev | sh
+
+    - name: Check out the source code
+      uses: actions/checkout@v2
+
+    - name: Test the project
+      run: |
+        cd src/top
+        # eldev -p -dtT -C test --expect 100
+        eldev -dtT -C compile --warnings-as-errors

.gitignore

@@ -3,5 +3,6 @@ _build/
 *.install
 *.elc
 .*.swp
+.eldev
 
 /result*

src/top/Eldev

@@ -0,0 +1 @@
+(eldev-use-package-archive 'melpa)