Docs: Add info about custom worlds (#5510)

* Cleaning up (#4)

Cleanup

* Added new paragraph for new games

* Update worlds/generic/docs/setup_en.md

Proofier-comitting

Co-authored-by: Exempt-Medic <60412657+Exempt-Medic@users.noreply.github.com>

* Added a mention in the header of the games page to refer to this guide if needed.

* Small tweaks

* Added mention regarding alternate version of worlds

* Update WebHostLib/templates/supportedGames.html

Co-authored-by: Exempt-Medic <60412657+Exempt-Medic@users.noreply.github.com>

* Update worlds/generic/docs/setup_en.md

Co-authored-by: Exempt-Medic <60412657+Exempt-Medic@users.noreply.github.com>

* Edits for comments

* Slight alternate versions rewording

* Edit subheadings

* Adjust link text

* Replace alternate versions section and reword first

---------

Co-authored-by: Danaël V <104455676+ReverM@users.noreply.github.com>
Co-authored-by: Rever <danael.villeneuve@gmail.com>
Co-authored-by: Exempt-Medic <60412657+Exempt-Medic@users.noreply.github.com>

WebHostLib/templates/supportedGames.html

@@ -31,6 +31,9 @@
     {% include 'header/oceanHeader.html' %}
     <div id="games" class="markdown">
         <h1>Currently Supported Games</h1>
+        <p>Below are the games that are currently included with the Archipelago software. To play a game that is not on
+        this page, please refer to the <a href="/tutorial/Archipelago/setup/en#playing-with-custom-worlds">playing with
+        custom worlds</a> section of the setup guide.</p>
         <div class="js-only">
             <label for="game-search">Search for your game below!</label><br />
             <div class="page-controls">

worlds/generic/docs/setup_en.md

@@ -136,6 +136,27 @@ are rolling locally, ensure this file is edited to your liking **before** rollin
 when running the Archipelago Installation software. If you have changed settings in this file, and would like to retain 
 them, you may rename the file to `options.yaml`. 
 
+### Playing with custom worlds
+
+If you are generating locally, you can play with worlds that are not included in the Archipelago installation.
+These worlds are packaged as `.apworld` files. To add a world to your installation, click the "Install APWorld" button
+in the launcher and select the `.apworld` file you wish to install. Alternatively, you can drag the `.apworld` file
+onto the launcher or double-click the file itself (if on Windows). Once the world is installed, it will function like
+the worlds that are already packaged with Archipelago. Also note that while generation with custom worlds must be done
+locally, these games can then be uploaded to the website for hosting and played as normal.
+
+We strongly recommend that you ensure the source of the `.apworld` is safe and trustworthy before playing with a
+custom world. Installed APWorlds are able to run custom code on your computer whenever you open Archipelago.
+
+#### Alternate versions of included worlds
+
+If you want to play with an alternate version of a game that is already included in Archipelago, you should also
+remove the original APWorld after completing the above installation. To do so, go to your Archipelago installation
+folder and navigate to the `lib/worlds` directory. Then move the `.apworld` or the folder corresponding to the game you
+want to play an alternate version of to somewhere else as a backup. If you want to play this original again, then
+restore the original version to `lib/worlds` and remove the alternate version, which is in the `custom_worlds` folder.
+
+Note: Currently, this cannot be done on the Linux AppImage release.
 
 ## Hosting an Archipelago Server