Add docker-compose for kiwix-server

added docker-compose for kiwix-server via docker-compose.yml.example which supports both local and remote zim file.
updated README.md to update about docker-compose.yml.example

docker/server/docker-compose.yml.example

@@ -0,0 +1,14 @@
+version: '3.3'
+services:
+  kiwix-serve:
+      ports:
+        - 8080:80
+      image: kiwix/kiwix-serve
+      # uncomment next 4 lines to use it with local zim file in /tmp/zim
+      # volumes:
+      #   - /tmp/zim:/data
+      # command:
+      #   - *.zim
+      # uncomment next 2 lines to use it with remote zim file
+      # environment:
+      #   - 'DOWNLOAD=https://download.kiwix.org/zim/wikipedia_bm_all.zim'