Update README.md

[arvindpandit27]

Added a new example for using the Mocking.jl package

[codecov]

Codecov Report

Merging #95 (a53394f) into master (9e93c88) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #95      +/-   ##
==========================================
+ Coverage   84.09%   84.12%   +0.03%     
==========================================
  Files           6        6              
  Lines         132      126       -6     
==========================================
- Hits          111      106       -5     
+ Misses         21       20       -1     

Impacted Files	Coverage Δ
src/expr.jl	100.00% <0.00%> (ø)
src/patch.jl	100.00% <0.00%> (ø)
src/dispatch.jl	100.00% <0.00%> (ø)
src/mock.jl	81.25% <0.00%> (+2.46%)	⬆️

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[omus]

Thanks. Could use some revision but I can see why having a more trivial example is useful

[omus]

I've updated the documentation to use Documenter instead of just the README. If you feel like this example is still useful feel free to re-open this PR with these changes to the index.md file.