Add attribute lists to CSpell ignoreRegExpList

CSpell (Code Spell Checker) supports custom ignore patterns that can be
added to the `ignoreRegExpList` in its `cspell.json` configuration file.
The configuration file previously was configured to ignore Markdown
fenced code blocks (like '```sh'), but not the extended Markdown syntax
used in Python Markdown attribute lists. These attribute lists are used
by Material for MkDocs to enable or disable code block copy behavior
(code blocks like '```{ .sh .no-copy }' added in 90f75b0).

This commit will update the `ignoreRegExpList` to ignore fenced code
blocks with attribute lists.

https://cspell.org/configuration/
streetsidesoftware/cspell#206
https://squidfunk.github.io/mkdocs-material/reference/code-blocks/

cspell.json

@@ -1,6 +1,6 @@
 {
   "ignorePaths": ["CHANGELOG.md", "**/*changelog.md"],
-  "ignoreRegExpList": ["/(```+)\\s?[a-z][\\s\\S]+?\\1/g", "/`([\\s\\S]+?)`/g"],
+  "ignoreRegExpList": ["/(`{3})[\\s\\S]+?\\1/g", "/`([\\s\\S]+?)`/g"],
   "languageSettings": [
     {
       "languageId": "python",