…static definitions

- setting better perf examples for devs

…finitions

+ update snapshots

squash with complex useMemo

+ remove conditional `let`

- the inline jsx creates a new component every rerender, this does not

- more granular breakup of memoized vars to reduce rerenders and increase readability

…act-window` to use it

- use new deep equal memoization hook to reduce rerenders on consumer-passed `sorting` and `sortingColumns`

- separate out memoized `sortedRowMap` to reduce dependencies/rerenders further

- rewrite `inMemoryRowIndices` more succinctly

- remove more inline jsx vars

- move fn utilities to bottom of file + wrap in `memo()`

- get rid of `cellContentProps` obj, just use props

- performance changes worked I guess!

- `sorting` is _only_ used by header cells, so it makes sense to waterfall it just to the header row instead of to all cells (which causes rerenders across every cell every time `sorting` from a consumer is referentially unstable)

+ rename sorting context to `sorted` to make the purpose of the context it clearer

+ reorder props list slightly (by usage etc)

+ return null earlier (which requires creating new component)

+ convert args to obj for easier reuse

+ clean up/convert tests to RTL, reduce snapshots