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/binary-search/README.md

@@ -0,0 +1,46 @@
+binary-search
+=============
+
+This is a really tiny, stupid, simple binary search library for Node.JS. We
+wrote it because existing solutions were bloated and incorrect.
+
+This version is a straight port of the Java version mentioned by Joshua Bloch
+in his article, [Nearly All Binary Searches and Merge Sorts are Broken](http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html).
+
+Thanks to [Conrad Irwin](https://github.com/ConradIrwin) and [Michael
+Marino](https://github.com/mgmarino) for, ironically, pointing out bugs.
+
+Example
+-------
+
+```js
+var bs = require("binary-search");
+
+bs([1, 2, 3, 4], 3, function(element, needle) { return element - needle; });
+// => 2
+
+bs([1, 2, 4, 5], 3, function(element, needle) { return element - needle; });
+// => -3
+```
+
+Be advised that passing in a comparator function is *required*. Since you're
+probably using one for your sort function anyway, this isn't a big deal.
+
+The comparator takes a 1st and 2nd argument of element and needle, respectively.
+
+The comparator also takes a 3rd and 4th argument, the current index and array,
+respectively. You shouldn't normally need the index or array to compare values,
+but it's there if you do.
+
+You may also, optionally, specify an input range as the final two parameters,
+in case you want to limit the search to a particular range of inputs. However,
+be advised that this is generally a bad idea (but sometimes bad ideas are
+necessary).
+
+License
+-------
+
+To the extent possible by law, The Dark Sky Company, LLC has [waived all
+copyright and related or neighboring rights][cc0] to this library.
+
+[cc0]: http://creativecommons.org/publicdomain/zero/1.0/