Strict getContents

[Li-yao Xia]

Hello Libraries,

In base, the functions which read all contents from a handle or file 
into one String currently all do lazy IO: readFile, getContents, 
hGetContents.

https://hackage.haskell.org/package/base-4.12.0.0/docs/System-IO.html#v:hGetContents

The easiest way to get a strict alternative seems to be to explicitly 
force the list, for example using ```length contents `seq` pure ()```, 
but that's far from an obvious solution.

Is there a better way?

If not, I propose to add readFile', getContents', hGetContents', which 
don't do lazy IO.

It regularly creates confusion among beginners, and it's easy to assume 
that lazy IO is benign if that's the only way to do certain operations, 
when it's arguably the wrong way to read files to begin with.

Cheers,
Li-yao