Fix links, add CI workflows

.github/remarkrc-linkchecker.yml

@@ -0,0 +1,2 @@
+plugins:
+  - remark-lint-are-links-valid-alive

.github/remarkrc-lint.yml

@@ -0,0 +1,3 @@
+plugins:
+  - remark-preset-lint-recommended
+  - remark-validate-links

.github/workflows/linkchecker.yml

@@ -0,0 +1,25 @@
+name: Link Checker
+on:
+  workflow_dispatch: {}
+
+jobs:
+  build:
+    name: Install and run link checker
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set Node.js
+        uses: actions/setup-node@v3
+        with:
+          node-version: 16.x
+
+      - name: Install yarn dependencies
+        uses: borales/actions-yarn@v4
+        with:
+          cmd: install # runs `yarn install`
+
+      - name: Run link checker
+        uses: borales/actions-yarn@v4
+        with:
+          cmd: run ci-link

.github/workflows/lint.yml

@@ -0,0 +1,25 @@
+name: Markdown Linter
+on:
+  pull_request: {}
+
+jobs:
+  build:
+    name: Install and run linter
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set Node.js
+        uses: actions/setup-node@v3
+        with:
+          node-version: 16.x
+
+      - name: Install yarn dependencies
+        uses: borales/actions-yarn@v4
+        with:
+          cmd: install # runs `yarn install`
+
+      - name: Run linter
+        uses: borales/actions-yarn@v4
+        with:
+          cmd: run ci-lint

package.json

@@ -1,14 +1,16 @@
 {
   "dependencies": {
-    "awesome-lint": "^0.10.0",
-    "remark": "^10.0.1",
-    "remark-cli": "^6.0.1",
-    "remark-lint": "^6.0.1",
+    "awesome-lint": "^1.2.0",
+    "remark": "^12.0.0",
+    "remark-cli": "^10.0.0",
+    "remark-lint": "^10.0.0",
     "remark-lint-are-links-valid-alive": "^0.3.0",
-    "remark-preset-lint-recommended": "^3.0.1",
-    "remark-validate-links": "^8.0.2"
+    "remark-preset-lint-recommended": "^7.0.0",
+    "remark-validate-links": "^13.0.2"
   },
   "scripts": {
+    "ci-lint": "node_modules/.bin/remark --frail --output /dev/null readme.md --rc-path .github/remarkrc-lint.yml",
+    "ci-link": "node_modules/.bin/remark --frail --output /dev/null readme.md --rc-path .github/remarkrc-linkchecker.yml",
     "lint-md": "node_modules/.bin/remark readme.md"
   },
   "remarkConfig": {