* Add markdownlint and markdownlint-github

* Update node version to 14

* Bump markdownlint-github

* Disable rules we don't currently care about

* cleanup

* Split markdownlint command per @jonrohan suggestion

* Split jobs

* fix: MD019/no-multiple-space-atx Multiple spaces after hash on atx style heading

* fix: MD045/no-alt-text Images should have alternate text (alt text)

* fix: MD001/heading-increment/header-increment Heading levels should only increment by one level at a time [Expected: h3; Actual: h4]

* fix: MD040/fenced-code-language Fenced code blocks should have a language specified

* fix: GH002/no-generic-link-text Avoid using generic link text like  or  [For link: here]

* fix: MD042/no-empty-links No empty links

* fix: MD036/no-emphasis-as-heading/no-emphasis-as-header Emphasis used instead of a heading

* fix: MD051/link-fragments Link fragments should be valid

* fix: MD024/no-duplicate-heading/no-duplicate-header Multiple headings with the same content