new icon: htmx (original, original-wordmark, plain, plain-wordmark, line, line-wordmark)

[weh]

Double check these details before you open a PR

• [x] PR does not match another non-stale PR currently opened
• [x] PR name matches the format new icon: Icon name (versions separated by comma). More details here
• [x] PR's base is the develop branch.
• [x] Your icons are inside a folder as seen here
• [x] SVG matches the standards laid out here
• [x] A new object is added in the devicon.json file as seen here

This PR closes #2071

Link to prove your SVG is correct and up-to-date.

• https://htmx.org/
• https://github.com/bigskysoftware/htmx/issues/1585