fix(lib/doc): fix jsdoc and typo

[dev-itsheng]

When I read Koa's source, I noticed some typo errors in JSDoc and documentation, so I tried to fix them.

[codecov[bot]]

Codecov Report

Merging #1662 (d2b4ebd) into master (00ce71f) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1662   +/-   ##
=======================================
  Coverage   99.60%   99.60%           
=======================================
  Files           5        5           
  Lines         507      507           
  Branches      142      142           
=======================================
  Hits          505      505           
  Misses          2        2           

Impacted Files	Coverage Δ
lib/request.js	100.00% <ø> (ø)
lib/response.js	100.00% <ø> (ø)

---

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 00ce71f...d2b4ebd. Read the comment docs.

[etroynov]

@hustLer2k @gxkl Hi,

Can you pls check this changes? Thx

[hustLer2k]

@fengmk2 could you review this PR please?