Added Dockerfile, Readme, .js script (#222)

* Added Dockerfile, Readme,  .js script
* Added develop folder to check.yml

develop/Dockerfile

@@ -0,0 +1,9 @@
+FROM onlyoffice/documentserver:latest
+RUN apt-get update -y && \ 
+	apt-get install git -y \
+			openjdk-11-jdk -y \
+			npm -y \
+			npm install -g grunt-cli -y && \
+	git clone --depth 1 https://github.com/ONLYOFFICE/build_tools.git var/www/onlyoffice/documentserver/build_tools && \
+	rm -rf /var/lib/apt/lists/*
+ENTRYPOINT python /var/www/onlyoffice/documentserver/build_tools/develop/run_build_js.py /var/www/onlyoffice/documentserver && /bin/sh -c /app/ds/run-document-server.sh 

develop/README.md

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+# Docker
+
+This directory containing instruction for developers,
+who want to change something in sdkjs or web-apps module,
+but don't want to compile pretty compilcated core product to make those changes.
+
+## Installing ONLYOFFICE Docs
+
+## How to use - Linux
+
+**Note**: You need the latest Docker version installed.
+
+You might need to pull **onlyoffice/documentserver** image:
+
+**Note**: Do not prefix docker command with sudo.
+[This](https://docs.docker.com/engine/install/linux-postinstall/#manage-docker-as-a-non-root-user)
+instruction show how to use docker without sudo.
+
+```bash
+docker pull onlyoffice/documentserver
+```
+
+### Create develop image
+
+To create a image with the ability to include external non-minified sdkjs code,
+use the following command from the dockerfile directory:
+
+```bash
+docker build -t documentserver-develop .
+```
+
+**Note**: The dot at the end is required.
+
+### Connecting external folders
+
+To connect external folders to the container,
+you need to pass the "-v" parameter
+along with the relative paths to the required folders.
+
+**For example, let's connect the external folders "sdkjs" and "web-apps" to the container:**
+
+```bash
+docker run -i -t -d -p 80:80 --restart=always \
+    -v /host-dir/sdkjs:/var/www/onlyoffice/documentserver/sdkjs \
+    -v /host-dir/web-apps:/var/www/onlyoffice/documentserver/web-apps documentserver-develop
+```

develop/run_build_js.py

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+#!/usr/bin/env python
+
+import sys
+sys.path.append(sys.argv[1] + '/build_tools/scripts')
+import build_js
+import config
+import base
+
+base.cmd_in_dir(sys.argv[1] + '/build_tools/', 'python', ['configure.py'])
+config.parse()
+
+build_js.build_js_develop(sys.argv[1])