DOC?MINOR: update .aspell.yml with configuration examples and comments

Expand the configuration file `.aspell.yml` to include detailed comments explaining the available settings such as mode, min_length, and ignoring identifiers. Also added commented-out examples for advanced features like fetching allowed words from a remote API and downloading dictionaries from GitHub/GitLab repositories or direct URLs. This makes it easier to understand and configure advanced spell-checking options.

Author: oktalz

.aspell.yml

@@ -1,7 +1,49 @@
+## Spell check scope: disabled (off), subject (first line only),
+## commit (full commit message), all (commit + file content)
+# mode: disabled | subject | commit | all
 mode: all
-min_length: 3
+
+## Minimum word length to spell-check (words shorter than this are skipped, default: 3)
+# min_length: 3
+
+## If true, code identifiers found in the diff will NOT be excluded from spell check
+# no_ignore_identifiers: false
+
+## File patterns to skip when mode is "all" (glob syntax)
 ignore_files:
   - '*test.go'
+
+## Extra words to accept as correctly spelled (one per line, case-insensitive)
 allowed:
   - mri
   - iid
+
+## Fetch an additional allowed-word list from a JSON API endpoint
+# remote_file:
+#   ## Direct URL to fetch
+#   url: "https://example.com/api/words"
+#   ## Or read the URL from this environment variable instead
+#   url_env: ALLOWED_WORDS_URL
+#   ## Set a custom HTTP header whose value is read from the named env var
+#   header_from_env: X-Custom-Header
+#   ## Set PRIVATE-TOKEN header from this env var (GitLab/GitHub auth)
+#   private_token_env: PRIVATE_TOKEN
+#   ## JSON key that contains the word list in the response
+#   allowed_items_key: words
+
+## Fetch dictionary files (.txt word lists or .rws aspell compiled dicts) from remote sources
+# dictionaries:
+#   ## Fetch every .txt/.rws file from a GitHub repo directory
+#   github:
+#     - url: "https://github.com/haproxytech/check-commit/tree/main/aspell/dictionaries"
+#       ## Optional env var holding a GitHub token (needed for private repos)
+#       token_env: GITHUB_TOKEN
+#   ## Fetch every .txt/.rws file from a GitLab repo directory (supports self-hosted instances)
+#   gitlab:
+#     - url: "https://gitlab.com/group/project/-/tree/main/path/to/dictionaries"
+#       ## Optional env var holding a GitLab private token (needed for private repos)
+#       token_env: GITLAB_TOKEN
+#   ## Fetch individual dictionary files by direct URL
+#   urls:
+#     - "https://raw.githubusercontent.com/haproxytech/check-commit/main/aspell/dictionaries/computing.txt"
+#     - "https://example.com/custom-words.txt"