Docs: Add section to Effects with guidance on which operator to use

[brandonroberts]

Other information:

Provide some clear documentation on which flattening operator to use for common tasks with Effects. There's 4 to choose from currently.

• concatMap
• exhaustMap
• mergeMap
• switchMap

May could include an example of how each operator behaves differently.

[alex-okrushko]

This article from @cartant can be also linked there: https://ncjamieson.com/avoiding-switchmap-related-bugs/

[jordanpowell88]

I'll work on this

[timdeschryver]

@jordanpowell88 before you do, please check with @brandonroberts . He might be working on this 😅

[jordanpowell88]

Ok, certainly @brandonroberts will do an excellent job writing this up

[david-shortman]

I'm up for working on this if it's not active

[Armenvardanyan95]

If this is still relevant, I can write a section on this

[brandonroberts]

Thanks @Armenvardanyan95, I'm still planning to take this one

[KylerJohnsonDev]

This is one of the most common issues I see with the implementation of NgRx. People tend to use switchMap even for database writes and, under the right circumstances, it causes subtle issues. @brandonroberts are you still planning to work on this? I'd be happy to take a crack at it.