Fix missing post imports in router docs example

[noxxxxxious]

Motivation

When going through the router docs, I noticed that some of the examples were using post but were not importing them (as if the import statement was copy pasted from a section that didn't use post).

Solution

Add the post import into the examples where it is being used.

[jplatte]

All the examples you modified are tested and work already. None of them use the free-standing post function, they all use the post method of MethodRouter.

[noxxxxxious]

Ah! Sorry about that! Thought I had caught something that was overlooked. Please pardon my noobiness.

[jplatte]

No worries.