[#372] Warn on usages ofreadFileText and writeFileText

[chshersh]

Resolves #372

Here is an example of exceptions:

chshersh@ubuntu:~$ cat test.txt 
Привет!

chshersh@ubuntu:~$ file --mime test.txt 
test.txt: text/plain; charset=utf-8

chshersh@ubuntu:~$ LANG=en_GB.UTF-16 cabal repl -b text
Resolving dependencies...
Build profile: -w ghc-9.2.1 -O1
In order, the following will be built (use -v for more details):
 - fake-package-0 (lib) (first run)
Configuring library for fake-package-0..
Preprocessing library for fake-package-0..
Warning: No exposed modules
GHCi, version 9.2.1: https://www.haskell.org/ghc/  :? for help

ghci> readFile "test.txt" 
"*** Exception: test.txt: hGetContents: invalid argument (invalid byte sequence)
ghci> import qualified Data.Text.IO as TIO
ghci> TIO.readFile "test.txt" 
*** Exception: test.txt: hGetContents: invalid argument (invalid byte sequence)
ghci> import qualified Data.Text.Lazy.IO as LTIO
ghci> LTIO.readFile "test.txt" 
"*** Exception: test.txt: hGetContents: invalid argument (invalid byte sequence)

[chshersh]

Using list of strings here to display on different lines as written in docs:

• https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/pragmas.html#warning-and-deprecated-pragmas

Example:

[vrom911]

Awesome!