docs: add document for maintainance

MAINTAINANCE.md

@@ -0,0 +1,33 @@
+# Release process
+
+If you don't have `bmp` command installed, first install `bmp` ruby gem:
+
+    gem install bmp
+
+When master is ready for the next release, hit the command:
+
+    bmp -p
+
+This automatically updates all the version numbers with a new one in the repository.
+
+Then hit the command:
+
+    npm run dist
+
+This builds the scripts and stylesheets. Then hit:
+
+    bmp -c
+
+This commits all the changes (including the built assets) and git-tags a new version (like v0.4.16):
+
+Then publish it to the npm registry (you need admin access to c3 module):
+
+    npm publish
+
+At this point, the new version is available through npm.
+
+Then push master and the tag to github:
+
+    git push origin master vX.Y.Z
+
+That's all.