Add CI and add explicit dependency versioning to all workflows

.github/workflows/ci.yml

@@ -0,0 +1,19 @@
+name: Crystal CI
+on:
+  push:
+  pull_request:
+    branches: [ "main" ]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20.x
+      - uses: crystal-lang/install-crystal@v1
+        with:
+          crystal: 1.6.2
+      - name: Download source
+        uses: actions/checkout@v4
+      - name: Run tests
+        run: crystal spec

.github/workflows/docs.yml

@@ -25,11 +25,14 @@ jobs:
 
     runs-on: ubuntu-latest
 
-    container:
-      image: crystallang/crystal
-
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/setup-node@v4
+      with:
+        node-version: 20.x
+    - uses: crystal-lang/install-crystal@v1
+      with:
+        crystal: 1.6.2
+    - uses: actions/checkout@v4
     - name: Generate docs
       run: crystal docs
     - name: Move docs to _site