Add codespell CI with configuration and fix existing typos

.codespellrc

@@ -0,0 +1,8 @@
+[codespell]
+# Ref: https://github.com/codespell-project/codespell#using-a-config-file
+skip = .git,.git-meta,.gitignore,.gitattributes,package-lock.json,*.lock,*.css,*.min.*,.codespellrc,*/spec/sites/*
+check-hidden = true
+# ignore-regex =
+ignore-words-list =
+  # nd - ordinal suffix in regex patterns like (st|nd|rd|th)
+  nd

.github/workflows/codespell.yml

@@ -0,0 +1,23 @@
+# Codespell configuration is within .codespellrc
+---
+name: Codespell
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+permissions:
+  contents: read
+
+jobs:
+  codespell:
+    name: Check for spelling errors
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Codespell
+        uses: codespell-project/actions-codespell@8f01853be192eb0f849a5c7d721450e7a467c579  # v2.2

INSTALLATION.md

@@ -42,7 +42,7 @@ gem install sitediff -v '1.2.1'
 ## Docker
 
 There is a `Dockerfile` in the root of the SiteDiff git repository. It uses
-the Docker offical Ruby image. Note that SiteDiff will use port `13080` for the result server. The following Docker image tags are available to be pulled.
+the Docker official Ruby image. Note that SiteDiff will use port `13080` for the result server. The following Docker image tags are available to be pulled.
 
 * latest (master branch)
 * 1.0.0

README.md

@@ -30,7 +30,7 @@
     - [ignore_whitespace](#ignore_whitespace)
     - [remove_html_comments](#remove_html_comments)
     - [before / after](#before--after)
-    - [includes](#incudes)
+    - [includes](#includes)
     - [dom_transform](#dom_transform)
         - [remove](#remove)
         - [strip](#strip)

config/sitediff.example.yaml

@@ -46,7 +46,7 @@ selector: 'body'
 
 # General regular expression rules, applied to both versions of the site.
 sanitization:
-  # Normalize input tags containg random tokens.
+  # Normalize input tags containing random tokens.
   - title: Remove form-build-id
     pattern: '<input type="hidden" name="form_build_id" value="form-[a-zA-Z0-9_-]+" *\/?>'
     substitute: '<input type="hidden" name="form_build_id" value="__form_build_id__">'

lib/sitediff/api.rb

@@ -20,7 +20,7 @@ def initialize(directory, config_file = nil)
     end
 
     ##
-    # Intialize a SiteDiff project.
+    # Initialize a SiteDiff project.
     #
     # Calling:
     #     SiteDiff::Api.init(