Add link to new video learning site

Author: crandmck

docs/community.md

@@ -42,6 +42,10 @@ These related projects may be of interest, but the CAI team doesn't maintain or
 
 The CAI maintains a [Discord server](https://discord.gg/CAI) for open technical discussions within the developer community, with channels focused on different projects and topics.
 
+## C2PA Foundations videos
+
+For a series of educational videos, see [C2PA Foundations](http://learn.contentauthenticity.org/).
+
 ## Other resources
 
 - **Read the [CAI blog](https://contentauthenticity.org/blog)** to get the latest news and updates about CAI.

docs/introduction.mdx

@@ -6,12 +6,14 @@ title: CAI open source SDK
 import cr_pin from '../static/img/cr-pin.png';
 import cai_open_source_red from '../static/img/cai-open-source-red.jpg';
 
-:::tip
 You're strongly encouraged to read this introduction and [Getting started](getting-started.mdx) to give you some basic background and context, before you dive right into development. [Working with manifests](manifest/understanding.md) also has some crucial information, regardless of which language and library you use.
-:::
 
 The Coalition for Content Provenance and Authenticity (C2PA) and Content Authenticity Initiative (CAI) are groups working together to develop and promote adoption of an open industry standard for content authenticity and provenance.
 
+:::tip See also
+For a series of educational videos on using the CAI open source SDK, see [**C2PA Foundations**](http://learn.contentauthenticity.org/).
+:::
+
 ## What's in the SDK
 
 The CAI open-source SDK (software development kit) is a set of tools and libraries that enable developers to create, verify, and display Content Credentials based on C2PA standards.

docusaurus.config.js

@@ -174,13 +174,11 @@ const config = {
             position: 'right',
             className: 'header-logo header-github-link',
           },
-          /*
           {
-            href: 'https://twitter.com/ContentAuth',
+            href: 'http://learn.contentauthenticity.org/',
             position: 'right',
-            className: 'header-logo header-twitter-link',
+            className: 'header-logo header-learn-link',
           },
-          */
         ],
       },
       footer: {

src/css/custom.css

@@ -112,6 +112,16 @@ a.hash-link {
   background: url("data:image/svg+xml,%3Csvg width='24' height='24' viewBox='0 0 71 55' fill='none' xmlns='http://www.w3.org/2000/svg'%3E%3Cg clip-path='url(%23a)'%3E%3Cpath d='M60.105 4.898A58.55 58.55 0 0 0 45.653.415a.22.22 0 0 0-.233.11 40.784 40.784 0 0 0-1.8 3.697c-5.456-.817-10.886-.817-16.23 0-.485-1.164-1.201-2.587-1.828-3.697a.228.228 0 0 0-.233-.11 58.386 58.386 0 0 0-14.451 4.483.207.207 0 0 0-.095.082C1.578 18.73-.944 32.144.293 45.39a.244.244 0 0 0 .093.167c6.073 4.46 11.955 7.167 17.729 8.962a.23.23 0 0 0 .249-.082 42.08 42.08 0 0 0 3.627-5.9.225.225 0 0 0-.123-.312 38.772 38.772 0 0 1-5.539-2.64.228.228 0 0 1-.022-.378c.372-.279.744-.569 1.1-.862a.22.22 0 0 1 .23-.03c11.619 5.304 24.198 5.304 35.68 0a.219.219 0 0 1 .233.027c.356.293.728.586 1.103.865a.228.228 0 0 1-.02.378 36.384 36.384 0 0 1-5.54 2.637.227.227 0 0 0-.121.315 47.249 47.249 0 0 0 3.624 5.897.225.225 0 0 0 .249.084c5.801-1.794 11.684-4.502 17.757-8.961a.228.228 0 0 0 .092-.164c1.48-15.315-2.48-28.618-10.497-40.412a.18.18 0 0 0-.093-.084Zm-36.38 32.427c-3.497 0-6.38-3.211-6.38-7.156 0-3.944 2.827-7.156 6.38-7.156 3.583 0 6.438 3.24 6.382 7.156 0 3.945-2.827 7.156-6.381 7.156Zm23.593 0c-3.498 0-6.38-3.211-6.38-7.156 0-3.944 2.826-7.156 6.38-7.156 3.582 0 6.437 3.24 6.38 7.156 0 3.945-2.798 7.156-6.38 7.156Z' fill='%232680eb'/%3E%3C/g%3E%3Cdefs%3E%3CclipPath id='a'%3E%3Cpath fill='%23fff' d='M0 0h71v55H0z'/%3E%3C/clipPath%3E%3C/defs%3E%3C/svg%3E")
     no-repeat;
 }
+
+.header-learn-link:before {
+  content: '';
+  width: 24px;
+  height: 24px;
+  display: flex;
+  background: url("data:image/svg+xml,%3Csvg width='24' height='24' viewBox='0 0 20 20' fill='none' xmlns='http://www.w3.org/2000/svg'%3E%3Cg clip-path='url(%23a)'%3E%3Cpath d='M0 4c0-1.1.9-2 2-2h16a2 2 0 0 1 2 2v12a2 2 0 0 1-2 2H2a2 2 0 0 1-2-2V4zm6 0v12h8V4H6zM2 5v2h2V5H2zm0 4v2h2V9H2zm0 4v2h2v-2H2zm14-8v2h2V5h-2zm0 4v2h2V9h-2zm0 4v2h2v-2h-2zM8 7l5 3l-5 3V7z' fill='%232680eb'/%3E%3C/g%3E%3Cdefs%3E%3CclipPath id='a'%3E%3Cpath fill='%23fff' d='M0 0h71v55H0z'/%3E%3C/clipPath%3E%3C/defs%3E%3C/svg%3E")
+    no-repeat;
+}
+
 .header-twitter-link:before {
   content: '';
   width: 24px;