Add PHP Decimal extension support

DOCUMENTATION/content/documentation/index.md

@@ -2291,6 +2291,20 @@ AST exposes the abstract syntax tree generated by PHP 7+. This extension is requ
 **Note** If you need a specific version of AST then search for the `WORKSPACE_AST_VERSION` argument under the Workspace Container and set it to the desired version and continue step 4.
 
 
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+<a name="Install-PHP-Decimal"></a>
+## Install PHP Decimal extension
+The PHP Decimal extension adds support for correctly-rounded, arbitrary-precision decimal floating point arithmetic. Applications that rely on accurate numbers (ie. money, measurements, or mathematics) can use Decimal instead of float or string to represent numerical values.
+
+For more information visit the [PHP Decimal website](https://php-decimal.io).
+
+2 - Search for the `WORKSPACE_INSTALL_PHPDECIMAL` argument under the Workspace Container
+
+2 - Search for the `PHP_FPM_INSTALL_PHPDECIMAL` argument under the PHP-FPM container
+
+3 - Set it to `true`
+
+4 - Re-build the container `docker-compose build workspace php-fpm`
 
 
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