Update md files

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 **Actively maintained**
 
-+ [Version 2.0.*](#version-20)
++ [Version 2.x](#version-2x)
 
 **No longer supported**
 
@@ -14,7 +14,7 @@
 
 ------
 
-## Version 2.0.*
+## Version 2.x
 
 - Major Release - ThemeManager Version 2
 - An upgrade from the previous 1.x is **NOT possible and NOT recommended**.
@@ -30,7 +30,8 @@ this documentation on how to [restore from a backup](https://docs.contao.org/man
 
 #### Global / Quality of Life Changes
 
-- Simultaneous support for Contao 4.13.x, 5.1.x, 5.2.x
+- Simultaneous support for Contao 4.13 and 5.3
+- Use Twig templates
 - Complete rewrite of the framework to use [CSS custom properties](https://developer.mozilla.org/en-US/docs/Web/CSS/--*)
 - Configure images within the filesystem as backgrounds and automatically generate the CSS after compiling
 - Prefilled layout settings when creating a new layout

UPGRADE.md

@@ -1,10 +1,71 @@
 # Upgrading contao-thememanager
 
++ [Version 2.0.* to ^2.1.*](#version-20-to-21)
 + [Version 1.* to 2.*](#version-1-to-2)
 
 _____
 
 
+## Version 2.0.* to ^2.1.*
+
+### Twig
+
+> [!IMPORTANT]  
+> If you have overwritten the HTML-Templates for following contao components, you'll have to rewrite them into twig.
+> Getting used to twig right now is the best long-term goal to provide proper updates from contao elements without
+> relying on modifying too many tempplates.
+>
+> ```php
+> \Contao\ContentHeadline::class;
+> \Contao\ContentList::class;
+> \Contao\ContentText::class;
+> \Contao\ContentTable::class;
+> \Contao\ContentHyperlink::class;
+> \Contao\ContentToplink::class;
+> \Contao\ContentImage::class;
+> \Contao\ContentGallery::class;
+> \Contao\ContentPlayer::class;
+> \Contao\ContentYouTube::class;
+> \Contao\ContentVimeo::class;
+> \Contao\ContentDownloads::class;
+> \Contao\ContentDownload::class;
+> \Contao\ContentTeaser::class;
+
+### I want to go back to HTML5
+
+Please refer to the upgrade.md from Contao to if you want to restore the classes or install plugins like:
+
+https://github.com/zoglo/contao-legacy-templates
+
+### Classnames
+
+The legacy `.ce_*`-classnames are reintroduced into the Twig-Templates. Please refer to the new ones in your own skin as
+they will be removed in version 2.2.
+
+| old class    | new class         |
+|--------------|-------------------|
+| ce_headline  | content-headline  |
+| ce_list      | content-list      |
+| ce_text      | content-text      |
+| ce_table     | content-table     |
+| ce_hyperlink | content-hyperlink |
+| ce_toplink   | content-toplink   |
+| ce_image     | content-image     |
+| ce_gallery   | content-gallery   |
+| ce_player    | content-player    |
+| ce_youtube   | content-youtube   |
+| ce_vimeo     | content-vimeo     |
+| ce_downloads | content-downloads |
+| ce_download  | content-download  |
+| ce_teaser    | content-teaser    |
+
+### Structure changes
+
+The gallery element does not use `div` anymore and follows the original `ul` style - Grid lists work like before.
+
+_____
+
+
 ## Version 1.* to 2.*
 
 > Upgrading from version 1.* to 2.* is