feat: dotenv integration

[nicetomytyuk]

Added dotenv import in service.js and changed readme in the way to let the user understand on how to set a custom connection string by using .env file.

Removed 16-17-18 from readme as it's repeated in 39-40

resolved #20

[codecov[bot]]

Codecov Report

Merging #21 (401493e) into master (55a43bd) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #21   +/-   ##
=======================================
  Coverage   97.98%   97.99%           
=======================================
  Files           8        8           
  Lines         398      399    +1     
=======================================
+ Hits          390      391    +1     
  Misses          8        8           

Impacted Files	Coverage Δ
src/service.js	95.83% <100.00%> (+0.05%)	:arrow_up:

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[nicetomytyuk]

@astagi just solved em' check it out 🎊

[astagi]

Merged! Thank you @nicetomytyuk 🙌