Split the examples into subfolders

.examples/dockerfiles/imap/apache/Dockerfile

@@ -1,4 +1,5 @@
 FROM nextcloud:apache
+
 RUN apt-get update \
  && apt-get install -y libc-client-dev libkrb5-dev \
  && rm -rf /var/lib/apt/lists/* \

.examples/dockerfiles/smb/apache/Dockerfile

@@ -1,2 +1,3 @@
 FROM nextcloud:apache
+
 RUN apt-get update && apt-get install -y smbclient && rm -rf /var/lib/apt/lists/*