General plugin development HOWTO

https://mariadb.com/docs/server/reference/product-development/plugin-development/development-writing-plugins-for-mariadb should be rewritten.

It should contain a general plugin development HOWTO, including:

• Set up the development tools needed
• Start a new plugin project: boilerplate etc.
• Compile a plugin project
• Debug and test a plugin
• Package the plugin project
• Publish the plugin project
• Do updates and bugfixing on a plugin project