[CI] add spell-check action for checking spelling, grammar, etc.

.codespellrc

@@ -0,0 +1,9 @@
+# Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/spell-check/.codespellrc
+# See: https://github.com/codespell-project/codespell#using-a-config-file
+[codespell]
+# In the event of a false positive, add the problematic word, in all lowercase, to a comma-separated list here:
+ignore-words-list = ,
+skip = ./.git,./.licenses,__pycache__,node_modules,./go.mod,./go.sum,./package-lock.json,./poetry.lock,./yarn.lock
+builtin = clear,informal,en-GB_to_en-US
+check-filenames =
+check-hidden =

.github/workflows/spell-check.yml

@@ -0,0 +1,22 @@
+name: Spell Check
+
+# See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
+on:
+  push:
+  pull_request:
+  schedule:
+    # Run every Tuesday at 8 AM UTC to catch new misspelling detections resulting from dictionary updates.
+    - cron: "0 8 * * TUE"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  spellcheck:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Spell check
+        uses: codespell-project/actions-codespell@master

README.md

@@ -1,6 +1,7 @@
 :floppy_disk: `portentax8-stm32h7-fw`
 =====================================
 [![Smoke test status](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/smoke-test.yml/badge.svg)](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/smoke-test.yml)
+[![Spell Check status](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/spell-check.yml/badge.svg)](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/spell-check.yml)
 [![Sync Labels status](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/sync-labels.yml/badge.svg)](https://github.com/arduino/portentax8-stm32h7-fw/actions/workflows/sync-labels.yml)
 
 This repository contains the firmware running on the `STM32H747AIIX`/Cortex-M7 core which, in combination with loadable kernel modules within the Linux distribution, provides access to various IO busses on the expansion headers of the Portenta X8.