Add docs for how to use external links

related to #360

app/web/src/components/EncodedUrl/ExternalScript.tsx

@@ -63,7 +63,7 @@ const ExternalScript = () => {
         CadHub url for this resource.{' '}
         <OutBound
           className="underline text-gray-500"
-          to="TODO learn.cadhub link"
+          to="https://learn.cadhub.xyz/docs/general-cadhub/external-resource-url"
         >
           Learn more
         </OutBound>{' '}

docs/docs/general-cadhub/external-resource-url.mdx

@@ -0,0 +1,37 @@
+---
+title: External resoure URLs
+---
+
+import Image from '@theme/IdealImage';
+
+import spaceDonut from '../../static/img/general-cadhub/space-donut.png';
+import openscadSelect from '../../static/img/getting-started/openscad-select.jpg';
+import externalScript1 from '../../static/img/general-cadhub/external-script-1.png';
+import externalScript2 from '../../static/img/general-cadhub/external-script-2.png';
+
+CadHub allows you to generate a URL that links to a script hosted on an external URL.
+The typical usecase for this as a CodeCad script hosted on github, this way the repo can continue to update and the link will stay up-to-date.
+Any URL that returns the script as plain text will work.
+
+Here's how to use it using github as an example.
+Find the file you want on Github, in this case ToastedIce's [space donut](https://github.com/toastedice/random_openscad_creations_I_made/blob/main/donut/spacedonut.scad).
+
+<Image img={spaceDonut} style={{backgroundSize: 'contain', paddingBottom: '2rem'}} />
+
+Copy the URL.
+
+Open the IDE for the Cad package to match your script, in this case OpenSCAD.
+
+<Image img={openscadSelect} style={{backgroundSize: 'contain', paddingBottom: '2rem', width: '400px', margin: '0 auto'}} />
+
+Click the share button in the top right, then select the "external srcipt" tab.
+
+<Image img={externalScript1} style={{backgroundSize: 'contain', paddingBottom: '2rem', width: '400px', margin: '0 auto'}} />
+
+Paste in the Github URL.
+
+<Image img={externalScript2} style={{backgroundSize: 'contain', paddingBottom: '2rem', width: '400px', margin: '0 auto'}} />
+
+From there you can copy the generated URL, or "copy and Render" to check the script is working as intended.
+
+Here's the [URL](http://cadhub.xyz/dev-ide/cadQuery#fetch_text_v1=https%3A%2F%2Fraw.githubusercontent.com%2Ftoastedice%2Frandom_openscad_creations_I_made%2Fmain%2Fdonut%2Fspacedonut.scad) from this example.

docs/sidebars.js

@@ -27,5 +27,6 @@ module.exports = {
         'round-anything/radii-conflict',
       ],
     },
+    'general-cadhub/external-resource-url'
   ],
 }