feat: support load typescript file

[sabakugaara]

Checklist

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

Affected core subsystem(s)

Description of change

[sabakugaara]

code from: https://github.com/eggjs/egg-rest/pull/21, fix lint error

[codecov[bot]]

Codecov Report

Merging #23 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #23   +/-   ##
=======================================
  Coverage   96.75%   96.75%           
=======================================
  Files           5        5           
  Lines         185      185           
=======================================
  Hits          179      179           
  Misses          6        6

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

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[atian25]

这 2 个 PR 的关系是？

那边还有几个 Review 问题还没解决

[sabakugaara]

这 2 个 PR 的关系是？

那边还有几个 Review 问题还没解决

代码是一样的，只有一个 lint 问题修复了，但是看原作者好像没打算继续更新。 所以，建议在这个分支上继续

[atian25]

@whxaxes 看下

[sabakugaara]

ping @whxaxes

[whxaxes]

补一下单测