feat: add types declaration

[jefrydco]

Close #15

[codecov]

Codecov Report

Merging #27 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #27   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines           20        20           
  Branches         3         3           
=========================================
  Hits            20        20           

---

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 0cd2a66...bbc634d. Read the comment docs.

[atinux]

Thanks @jefrydco