Run typos on CI

Typos[^1] is a source code spell checker with low false positive rate,
designed to be run on CI. I wouldn't lie, it does sound intriguing.
Let's try it and see how it goes.

[^1]: https://github.com/crate-ci/typos

.github/workflows/ci.yml

@@ -7,6 +7,15 @@ on:
     branches: [master]
 
 jobs:
+  typo:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Check spelling of file.txt
+        uses: crate-ci/typos@master
+
   lint:
     runs-on: ubuntu-latest
     steps: