Docs: Add conceptual docs for advanced development topics [UXR]

[josmperez]

Incorporate feedback such as:

• Wants more docs for understanding concepts.
• Doesn’t want more step by step docs because they’re mostly good only for beginners, but they want explanations of more advanced features. They had to rely on source code to understand advanced functions.
• Examples of advanced topics:
  Wants better docs on annotation support on backend.
  Wants better docs on creating a plugin that can work with alerting, and how data frames can be used with alerting.
  Suggests that we improve doc on using create-plugin because forum posts were outdated on how to use Go to support order of map data type.
  Had to contact support about plugin options. There’s a Getting Started guide, but doesn’t document the option parameters. Should have the code on GitHub, but would be better if there were a documented version of the code.
  Had difficulty with establishing database connector, and used tutorials. Could use more detail in tutorials. Needed to have a mental model of how everything fit together.
  There’s both an HTML input component and a code input component, he didn’t know about both. No info that says that if you want to enter SQL, etc., then use the code component.

Note this issue is a draft that will need to be broken into subtasks or separate issues.