documentation: Creates a short documentation for vchat

I ran into issues figuring out why modifying vchat.js did not cause changes to the game when the last PR I saw modifying it did nothing else (about may, 2022). Turns out, in september 2022 - minification was done.

This readme instructs developers to do so to avoid future confusion and explains how.

I also made a note about keeping ss13styles.css sync'd with stylesheet.dm

code/modules/vchat/README.md

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+# VChat
+(Please add to this file as you learn how this thing works. Thank you!)
+## Development
+
+To implement changes to VChat, one must modify either vchat.js or vchat_client,
+ where vchat.js corresponds to what actually appears to the user.
+ Not all of the logic is isolated within vchat_client, vchat.js handles a significant amount of processing as well.
+
+### vchat.js
+
+vchat.js is a development file - it is not actually included in the actual game code. Instead, what the game expects is
+the minified version "vchat.min.js"
+
+Therefore, to have your changes in "vchat.js" apply to the game for either PR or testing - you must first minify your script.
+If you are unfamiliar how to, simply you copy the file contants in vchat.js, paste them into https://codebeautify.org/minify-js
+or any similar tool and paste its output into vchat.min.js .
+
+As of 2023/08/05, no tool is provided by the codebase to handle minification for the developer.
+
+### ss13styles.css
+
+Handles chat colours, background colours, filtering.
+
+Please keep this file synchronized with code\stylesheet.dm where possible (filters, lightmode colours).