miss build.md

Author: gxthrj

build.md

@@ -0,0 +1,16 @@
+## Build an image from source
+
+**Docker images are not official ASF releases but provided for convenience. Recommended usage is always to build the source.**
+
+1. install release version (Apache releases are beginning from version 0.9):
+```
+# Assign Apache release version number to variable `APISIX_VERSION`, for example: 1.2 . The latest version can be find at `https://github.com/apache/incubator-apisix/releases`
+
+APISIX_VERSION=1.2
+docker build -t apisix:${APISIX_VERSION}-alpine --build-arg APISIX_VERSION=${APISIX_VERSION} -f alpine/Dockerfile alpine
+```
+
+2. install master branch version, which has latest code(ONLY for the developer's convenience):
+```
+docker build -t apisix:master-alpine -f alpine/Dockerfile alpine
+```