Expose all recipe interface functions for each recipe

[rishabhpoddar]

• If a recipe interface has 5 functions, we should expose all of them via the recipe's index.ts file so that the user can call them manually if they want.
• Also change this guide to say that this needs to be done for any new recipe
• Change to docs as well.

[rishabhpoddar]

Closing in favour of https://github.com/supertokens/for-zenhub/issues/28