Add contact backend and update readme

Dockerfile

@@ -1,5 +1,6 @@
 FROM ghcr.io/gohugoio/hugo:v0.160.0 AS build
-
+ARG CONTACT_FORM_URL
+ENV CONTACT_FORM_URL $CONTACT_FORM_URL
 WORKDIR /project
 COPY . /project
 RUN hugo build --minify --cleanDestinationDir