Added how build Vanilla

Author: atelomycterus

README.md

@@ -29,3 +29,7 @@ installation.These variables are mandatory.
 ## Setup Vanilla Forums 
 
 Go to [Setup Vanilla Forums](./docs/SetupVanillaForums.md) to complete installation.
+
+## Build Vanilla Forums
+
+Go to [Build Vanilla Forums](./docs/BuildVanillaForums.md) to install dependencies and build assets. 

docs/BuildVanillaForums.md

@@ -0,0 +1,52 @@
+# Build Vanilla Forums
+
+Vanilla Forums has pre-built frontend assets (js, css and addons assets).
+
+The full source code is https://github.com/vanilla/vanilla/tree/Vanilla_3.3.
+
+## Requirements
+
+- Node.js “>=8.0.0 <12.0.0”
+- PHP 7.2 - 7.4 (as of Vanilla 3.3)
+- Yarn
+- Composer 
+
+## Installing yarn
+
+Install yarn:
+ 
+`npm install -g yarn`
+
+## Installing composer
+
+Install composer:
+
+`php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"`
+
+`php -r "if (hash_file('sha384', 'composer-setup.php') === '756890a4488ce9024fc62c56153228907f1545c228516cbf63f885e036d37e9a59d27d63f46af1d4d07ee0f76181c7d3') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"`
+
+`php composer-setup.php`
+
+`php -r "unlink('composer-setup.php');"`
+
+
+## Building Frontend assets
+ 
+1.Clone or download a repo. Go to the root folder: 
+cd `Vanilla_3.3`
+
+2.Run the command to install dependencies and build:
+`composer install or php composer.phar install`
+
+You should see output 
+
+![./images/build.png](./images/build.png)
+
+
+3.Copy all files from the 'dist' folder to 'forums/vanilla/dist' (the 'forums' repo). 
+
+Notes:
+The first time you run this, it may take a while. Subsequent runs should be faster, but if you are constantly 
+updating the javascript or CSS or addons or themes, it's recommended to use the developer build.
+
+`yarn build:dev`