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/color-convert/README.md

@@ -0,0 +1,57 @@
+# color-convert [![Build Status](https://travis-ci.org/harthur/color-convert.svg?branch=master)](https://travis-ci.org/harthur/color-convert)
+Color-convert is a color conversion library for JavaScript and node. It converts all ways between `rgb`, `hsl`, `hsv`, `hwb`, `cmyk`, and CSS keywords:
+
+```js
+var converter = require("color-convert")();
+
+converter.rgb(140, 200, 100).hsl()   // [96, 48, 59]
+
+converter.keyword("blue").rgb()      // [0, 0, 255]
+```
+
+# Install
+
+```console
+npm install color-convert
+```
+
+# API
+
+Color-convert exports a converter object with getter/setter methods for each color space. It caches conversions:
+
+```js
+var converter = require("color-convert")();
+
+converter.rgb(140, 200, 100).hsl()   // [96, 48, 59]
+
+converter.rgb([140, 200, 100])       // args can be an array
+```
+
+### Plain functions
+Get direct conversion functions with no fancy objects:
+
+```js
+require("color-convert").rgb2hsl([140, 200, 100]);   // [96, 48, 59]
+```
+
+### Unrounded
+To get the unrounded conversion, append `Raw` to the function name:
+
+```js
+convert.rgb2hslRaw([140, 200, 100]);   // [95.99999999999999, 47.619047619047606, 58.82352941176471]
+```
+
+### Hash
+There's also a hash of the conversion functions keyed first by the "from" color space, then by the "to" color space:
+
+```js
+convert["hsl"]["hsv"]([160, 0, 20]) == convert.hsl2hsv([160, 0, 20])
+```
+
+### Other spaces
+
+There are some conversions from rgb (sRGB) to XYZ and LAB too, available as `rgb2xyz()`, `rgb2lab()`, `xyz2rgb()`, and `xyz2lab()`.
+
+# Contribute
+
+Please fork, add conversions, figure out color profile stuff for XYZ, LAB, etc. This is meant to be a basic library that can be used by other libraries to wrap color calculations in some cool way.