reexport hFlush

[rektrex]

Resolves #314

Checklist:

HLint

• I've changed the exposed interface (add new reexports, remove reexports, rename reexported things, etc.).
  • I've updated hlint.dhall accordingly to my changes (add new rules for the new imports, remove old ones, when they are outdated, etc.).
  • I've generated the new .hlint.yaml file (see this instructions).

General

• I've updated the CHANGELOG with the short description of my latest changes.
• All new and existing tests pass.
• I keep the code style used in the files I've changed (see style-guide for more details).
• I've used the stylish-haskell file.
• My change requires the documentation updates.
  • I've updated the documentation accordingly.
• I've added the [ci skip] text to the docs-only related commit's name.

[hint-man]

There is no place for me here... I will choose the truth I like.

[chshersh]

@rektrex Thanks for your PR! Meanwhile, we've discussed a slightly better module structure with @vrom911, and we were thinking about reexporting more stuff that works with Handle from a separate Relude.Lifted.Handle module. If you are interested in what needs to be done and pushing this forward, we can discuss it under the corresponding issue first 🙂 Otherwise, don't worry! We can close this PR and take care of this issue by ourselves.

[chshersh]

Closing in favour of #323