Improve README.md examples

[qmuntal]

This PR updates the examples in the README.md to make it clear that the errors should be handled someway and also clarify hash function requirements.

Fixes #106

[codecov[bot]]

Codecov Report

Merging #111 (ebe4891) into main (66f9d81) will increase coverage by 2.04%. The diff coverage is 100.00%.

:exclamation: Current head ebe4891 differs from pull request most recent head e30ab45. Consider uploading reports for the commit e30ab45 to get more accurate results

@@            Coverage Diff             @@
##             main     #111      +/-   ##
==========================================
+ Coverage   89.74%   91.79%   +2.04%     
==========================================
  Files          10       10              
  Lines         985      975      -10     
==========================================
+ Hits          884      895      +11     
+ Misses         67       54      -13     
+ Partials       34       26       -8     

Impacted Files	Coverage Δ
headers.go	92.14% <100.00%> (-1.15%)	:arrow_down:
signer.go	100.00% <0.00%> (ø)
ed25519.go	100.00% <0.00%> (ø)
verifier.go	100.00% <0.00%> (ø)
sign.go	88.93% <0.00%> (+1.03%)	:arrow_up:
sign1.go	86.86% <0.00%> (+1.75%)	:arrow_up:
algorithm.go	100.00% <0.00%> (+3.44%)	:arrow_up:
ecdsa.go	95.89% <0.00%> (+19.32%)	:arrow_up:
rsa.go	100.00% <0.00%> (+25.00%)	:arrow_up:

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[qmuntal]

@yogeshbdeshpande can you take a look at this?

[qmuntal]

I don't have merge permissions, need someone to do that for me :)

[yogeshbdeshpande]

Done! and Thank you for the Excellent Work!