Documentation for Optimization Detective needs further fleshing out

[westonruter]

Previously: #1782, #1763

• How to write an extension
• Class reference
• JSON Schema
• Function reference
• Extract hooks docs for functions, hooks, and classes from PHPDoc? This could should include improved formatting of the accepted arguments to each action/filter.

[westonruter]

• Function reference
• Extract hooks docs for functions, hooks, and classes from PHPDoc? This could should include improved formatting of the accepted arguments to each action/filter.

To be addressed in #1894.