Update README.md

Author: beevelop

README.md

@@ -16,6 +16,10 @@
     + APIs: android-10,android-15,android-16,android-17,android-18,android-19,android-20,android-21,android-22,android-23,android-24,android-25
     + Build-Tools: 25.0.2
 
+----
+## Tagging scheme
+- `v${TOOLS_VERSION}-${BUILD_TOOLS_VERSION}-${HIGHEST_ANDROID_SDK_VERSION}`
+- e.g. `v25.2.5-27.0.0-26`
 ----
 ### Pull from Docker Hub
 ```