add a documentation for those who would like to hack this project

doc/HACKING.md

@@ -0,0 +1,9 @@
+# Hacking
+
+If you want to hack this package, you will have to:
+ - create an account on npmjs.com (https://www.npmjs.com/signup)
+ - enable 2FA in `auth-only` mode (https://docs.npmjs.com/getting-started/using-two-factor-authentication)
+ - generate a read-write token (https://docs.npmjs.com/getting-started/working_with_tokens)
+ - change the name of this package (so that it does not collide with my version on npmjs.com)
+ - publish it manually for the first time (`npm publish --tag testing`)
+ - change the version number each time you scratch your jenkins (`npm version patch`)