docs(upgrade): Prepares upgrade docs for v6 alpha. (#3885)

* docs(upgrade): Adds migration information for v6 release.

* Updates framework of upgrade docs for alpha release.

* Content updates.

* A few content updates.

* Update release-highlights.md

removed an extra "you"

* update tab order on PF6 upgrade page

* Add a couple links.

* Update instruction and rename penta.

* Update packages/documentation-site/patternfly-docs/content/get-started/release-highlights.md

* Update packages/documentation-site/patternfly-docs/content/get-started/release-highlights.md

* Update packages/documentation-site/patternfly-docs/content/get-started/release-highlights.md

* Makes updates to the class-name-updater info.

---------

Co-authored-by: Andrew Ronaldson <[email protected]>
Co-authored-by: nicolethoen <[email protected]>

Author: 3 people

packages/documentation-framework/routes.js

@@ -83,7 +83,9 @@ const sourceOrder = {
   html: 3,
   'html-demos': 4,
   'design-guidelines': 99,
-  'accessibility': 100
+  'accessibility': 100,
+  'upgrade-guide': 101,
+  'release-notes': 102,
 };
 
 const sortSources = ({ source: s1 }, { source: s2 }) => {