Add save svg-badge directly to gist

This adds the posibility of saving an SVG badge generated by the same
shields.io dirictly to the gist. Instead of prepering a JSON file to
be sent to their service, we use their library directly, which outputs
an SVG file that we can save to the user’s gist.

Filenames ending in `.svg` will use this library automatically.

Additionally there is a major refactoring where the older `node:http`
library has been swapped out for `fetch`.

Also swap from node 16 to node 20

fixes #24

node_modules/css-color-converter/CHANGELOG.md

@@ -0,0 +1,22 @@
+# 2.0.0 - 2020-09-24
+* Rewrite as ES module. Some breaking changes to the API surface has been made as a result.
+* Better adhere to CSS specification (#4).
+* Add support for CSS Color Module Level 4 syntax.
+* Update dependencies.
+* Add eslint.
+* Add babel. 
+
+# 1.1.1 - 2020-03-20
+* Fix alpha 0 incorrectly defaulting to 1 (#2). Thanks to jedwards1211.
+
+# 1.1.0 - 2016-08-13
+* Add `toHslaArray` method.
+
+# 1.0.2 - 2015-05-27
+* Fix typo causing `rgba()` to return incorrect results.
+
+# 1.0.1 - 2015-05-27
+* Fix `toHexString()` not padding values.
+
+# 1.0.0 - 2015-05-27
+* Initial release.