Add interface implements annotation

I want use `@interface`,  `@implements {Type}` annotation in my company projects.

these are Google Closure Compiler jsdoc annotations.

i heard that you want add this feature to 3.4.0 but we need this feature 

so i add some codes for this. please check.

thank you.
Minor comment: Where possible, use `toBe` (like `===`) rather than `toEqual` (like `==`).