Massive dependencies

[sjakobi]

I recently noticed the massive dependency tree that using interpolate incurs. By switching to neat-interpolation, I was able to remove the following transitive dependencies from hnix:

• haskell-src-exts
• haskell-src-meta
• safe
• th-expand-syns
• th-lift
• th-lift-instances
• th-orphans
• th-reify-many

I wonder whether this warrants a warning and/or a recommendation for neat-interpolation from the readme or package description.

My PR to update hnix is haskell-nix/hnix#635.