Substitute rainloop version in url with variable

Dockerfile

@@ -3,8 +3,8 @@ FROM php:7.4.12-apache
 ARG RAINLOOP_VERSION=1.14.0
 
 ARG DEBIAN_FRONTEND=noninteractive
-ARG RAINLOOP_URL=https://github.com/RainLoop/rainloop-webmail/releases/download/v1.14.0/rainloop-community-${RAINLOOP_VERSION}.zip
-ARG RAINLOOP_URL_ASC=https://github.com/RainLoop/rainloop-webmail/releases/download/v1.14.0/rainloop-community-${RAINLOOP_VERSION}.zip.asc
+ARG RAINLOOP_URL=https://github.com/RainLoop/rainloop-webmail/releases/download/v${RAINLOOP_VERSION}/rainloop-community-${RAINLOOP_VERSION}.zip
+ARG RAINLOOP_URL_ASC=https://github.com/RainLoop/rainloop-webmail/releases/download/v${RAINLOOP_VERSION}/rainloop-community-${RAINLOOP_VERSION}.zip.asc
 ARG RAINLOOP_PGP_PUBLIC_KEY=https://www.rainloop.net/repository/RainLoop.asc 
 ARG RAINLOOP_GPG_FINGERPRINT="3B79 7ECE 694F 3B7B 70F3  11A4 ED7C 49D9 87DA 4591"