Improve markdown linter customization

[Nana-EC]

Story Form

As a block node developer
I want to customize the linter used for markdown files
So that I can ensure consistent and clean documentation standards

Technical Notes

#886 introduced the .markdownlint.yml file.
A few suggestion were made in the PR but were not either out of scope or good ideas to revisit with more data or in a follow up PR so as not to overload the already large PR.

• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)
• docs: Centralizes docs in repo and suggests grouping structure #886 (comment)

These should be revisited in addition to any other improvements