WIP: adds hkt support

[sobolevn]

This is just a quick demo for ones who is interested.

[codecov]

Codecov Report

Merging #446 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #446   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           48        45    -3     
  Lines         1228      1298   +70     
  Branches       154       112   -42     
=========================================
+ Hits          1228      1298   +70     

Impacted Files	Coverage Δ
...eturns/_generated/futures/_reader_future_result.py	100.00% <ø> (ø)
returns/_generated/futures/_future.py	100.00% <100.00%> (ø)
returns/_generated/futures/_future_result.py	100.00% <100.00%> (ø)
returns/_generated/pipeline/flow.py	100.00% <100.00%> (ø)
returns/context/requires_context.py	100.00% <100.00%> (ø)
returns/context/requires_context_future_result.py	100.00% <100.00%> (ø)
returns/context/requires_context_ioresult.py	100.00% <100.00%> (ø)
returns/context/requires_context_result.py	100.00% <100.00%> (ø)
returns/future.py	100.00% <100.00%> (ø)
returns/interfaces/applicative.py	100.00% <100.00%> (ø)
... and 42 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b403300...dcab55d. Read the comment docs.

[sobolevn]

The only thing left to do is:

• add Rescuable interface with .rescue method
• add rescue method and pointfree function
• add ResultBased interface with .from_result and .bind_result methods
• add bind_result method and pointfree function