feat: support findOne

[ChieveiT]

Checklist

• [x] npm test passes
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added
• [x] commit message follows commit guidelines

Description of change

1. 15

2. I have changed the test case createCollection() && listCollections() because the error message have been changed from must pass name of collection to create to collection name has invalid type null in mongo 4.0.4

[codecov[bot]]

Codecov Report

Merging #25 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #25   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           3      3           
  Lines          91     93    +2     
=====================================
+ Hits           91     93    +2

Impacted Files	Coverage Δ
lib/mongo.js	100% <100%> (ø)	:arrow_up:

---

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 e1fe2f7...3e2e912. Read the comment docs.

[codecov[bot]]

Codecov Report

Merging #25 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #25   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           3      3           
  Lines          91     93    +2     
=====================================
+ Hits           91     93    +2

Impacted Files	Coverage Δ
lib/mongo.js	100% <100%> (ø)	:arrow_up:

---

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 e1fe2f7...3e2e912. Read the comment docs.