Add action to remind people to update DB readme (#2364)

# Description
So we don't need @MartinquaXD for comments like
[this](#2359 (comment))

Uses https://github.com/ethanis/nitpicker

# Changes
- [x] Add new step to existing workflow

## How to test
https://github.com/fleupold/weekly-release-action/pull/7

.github/nitpicks.yml

@@ -0,0 +1,4 @@
+- markdown: |
+    Reminder: Please update the DB Readme.
+  pathFilter:
+    - "database/sql/**"

.github/workflows/pull-request.yaml

@@ -25,6 +25,15 @@ jobs:
           cargo clippy --version
       - run: cargo +nightly fmt --all -- --check
       - run: cargo clippy --locked --workspace --all-features --all-targets -- -D warnings
+
+  nitpicker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ethanis/nitpicker@v1
+        with:
+          nitpicks: ".github/nitpicks.yml"
+          token: "${{ secrets.GITHUB_TOKEN }}"
 
   unit-tests:
     timeout-minutes: 60