Improvements + updates ✨

[3imed-jaberi]

• update .gitignore file 🐞 ..
• avoid generating package-lock.json ☔️ ..
• use xo over native eslint to lint 💅🏻 ..
• update LICENSE 🗝 ..
• use nyc over istanbul for coverage 💯 ..
• update mocha ☕️ ..
• update test code (support koa 1 and 2 + use koa-convert to switch) 🧪 ..
• update ci pipeline 🎲 ..
• remove some files ❌ ..
• improve the source code ✨ ..
• update README.md ( add some note + add one line of code) 📋 ..
• better pkg.json 🎗 ..

ready to next release 🚀 ..

[codecov]

Codecov Report

Merging #43 into master will increase coverage by 0.35%.
The diff coverage is 97.36%.

@@            Coverage Diff             @@
##           master      #43      +/-   ##
==========================================
+ Coverage   98.20%   98.56%   +0.35%     
==========================================
  Files           1        1              
  Lines         167      139      -28     
  Branches       35        0      -35     
==========================================
- Hits          164      137      -27     
+ Misses          3        2       -1     

Impacted Files	Coverage Δ
index.js	98.56% <97.36%> (+0.35%)	⬆️

---

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 ca9d0f9...2a14b95. Read the comment docs.

[3imed-jaberi]

@niftylettuce, kindly bro can you merge this PR then #45 and publish new version and close this issue #46