tools: add REPLACEME and DEP X checks to workflow

.github/workflows/lint-release-proposal.yml

@@ -57,3 +57,13 @@ jobs:
       - name: Verify NODE_VERSION_IS_RELEASE bit is correctly set
         run: |
           grep -q '^#define NODE_VERSION_IS_RELEASE 1$' src/node_version.h
+      - name: Check for placeholders in documentation
+        run: |
+          if grep -q "REPLACEME" doc/api/*.md; then
+            echo "Please update REPLACEME tags in doc/api/*.md files. See doc/contributing/releases.md."
+            exit 1
+          fi
+          if grep -q "DEP...X" doc/api/deprecations.md; then
+            echo "Please update DEP...X in doc/api/deprecations.md. See doc/contributing/releases.md."
+            exit 1
+          fi