added docker env for build image

Dockerfile

@@ -0,0 +1,44 @@
+FROM focker.ir/ubuntu:18.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && \
+    apt-get install -y \
+    build-essential \
+    bash \
+    bc \
+    binutils \
+    build-essential \
+    bzip2 \
+    cpio \
+    g++ \
+    gcc \
+    git \
+    gzip \
+    locales \
+    libncurses5-dev \
+    libdevmapper-dev \
+    libsystemd-dev \
+    make \
+    mercurial \
+    whois \
+    patch \
+    perl \
+    python \
+    rsync \
+    sed \
+    tar \
+    vim \ 
+    unzip \
+    wget \
+    bison \
+    flex \
+    libssl-dev \
+    libfdt-dev \
+    swig \
+    libncurses-dev \
+    libpython3-dev \
+    python3-distutils
+
+
+RUN ["/bin/bash"]

README.md

@@ -42,6 +42,18 @@ If you have a multicore CPU, you can try
 make -j ${YOUR_CPU_COUNT}
 ```
 
+## using docker environment for build
+build docker image build execute below command
+```shell
+sudo docker build -t buildroot-ubuntu18:latest .
+```
+after build docker image create docker container with belo command and follow build instruction:
+```shell
+sudo docker run -it --rm \
+  -v $PWD/buildroot-sinux/:/buildroot-sinux \
+  buildroot-ubuntu18:latest
+
+
 
 ## Flashing firmware to target
 ### WARNING: Please be careful when running the following commands, as you might destroy essential data or disk.