chore: replace require-lint with depcheck

Depcheck is more actively maintained and supports "node:" prefixes.
It also scans devDependencies which found unused modules.
However it can't tell if a prod module should have been a devDependency.

.depcheckrc.yml

@@ -0,0 +1,9 @@
+ignores:
+  # dynamically loaded themes
+  - "@thumbsup/theme-cards"
+  - "@thumbsup/theme-classic"
+  - "@thumbsup/theme-mosaic"
+  - "@thumbsup/theme-flow"
+  # to check
+  - "markdown-toc"
+  - "gm"

.requirelintrc

@@ -1 +0,0 @@
-ignore-extra=@thumbsup/theme-cards,@thumbsup/theme-classic,@thumbsup/theme-mosaic,@thumbsup/theme-flow

package.json

@@ -27,7 +27,7 @@
     "bin"
   ],
   "scripts": {
-    "pretest": "standard && require-lint",
+    "pretest": "standard && depcheck",
     "test": "c8 mocha"
   },
   "dependencies": {
@@ -63,13 +63,13 @@
   },
   "devDependencies": {
     "c8": "^8.0.1",
+    "depcheck": "^1.4.7",
     "glob": "^10.3.10",
     "gm": "^1.25.0",
     "markdown-toc": "^1.2.0",
     "mocha": "^10.2.0",
     "mock-fs": "^5.2.0",
     "mock-spawn": "^0.2.6",
-    "require-lint": "^2.0.3",
     "should": "^13.2.3",
     "sinon": "^17.0.1",
     "standard": "^17.1.0",