Add a CI workflow to check for commonly misspelled words

In the event of a false positive, the problematic word should be added, in all lowercase, to the `ignore-words-list`
field in ./.codespellrc.

Author: per1234

.codespellrc

@@ -0,0 +1,6 @@
+[codespell]
+# In the event of a false positive, add the problematic word, in all lowercase, here:
+ignore-words-list = afterall
+check-filenames =
+check-hidden =
+skip = ./.git,./dist

.github/workflows/spell-check.yml

@@ -0,0 +1,26 @@
+name: Spell Check
+
+on:
+  pull_request:
+  push:
+  schedule: # Schedule trigger for catching new misspelling detections resulting from dictionary updates.
+    # Run every Saturday at 3 AM UTC.
+    - cron: "0 3 * * 2"
+  # workflow_dispatch event allows the workflow to be triggered manually
+  # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows#workflow_dispatch
+  workflow_dispatch:
+  # repository_dispatch event allows the workflow to be triggered via the GitHub API
+  # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows#repository_dispatch
+  repository_dispatch:
+
+jobs:
+  spellcheck:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      # See: https://github.com/codespell-project/actions-codespell/blob/master/README.md
+      - name: Spell check
+        uses: codespell-project/actions-codespell@master

README.md

@@ -1,6 +1,7 @@
 # setup-arduino-cli
 
-[![Actions Status](https://github.com/arduino/setup-arduino-cli/workflows/Test%20Action/badge.svg)](https://github.com/arduino/setup-arduino-cli/actions)
+[![Tests Status](https://github.com/arduino/arduino-lint-action/workflows/Test%20Action/badge.svg)](https://github.com/arduino/arduino-lint-action/actions?workflow=Test+Action)
+[![Spellcheck Status](https://github.com/arduino/arduino-lint-action/workflows/Spell%20Check/badge.svg)](https://github.com/arduino/arduino-lint-action/actions?workflow=Spell+Check)
 
 This action makes the `arduino-cli` tool available to Workflows.