Update docs for Slate

```
android_coverage.cn.md
  1: h1 is missing
  18: `--` and `---` line breaks must not be used. Delete them.
  103: h4, h5, h6 should not be used. Use h1, h2 or h3.

caps.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead
  13: `--` and `---` line breaks must not be used. Delete them.
  15: h4, h5, h6 should not be used. Use h1, h2 or h3.
  25: `--` and `---` line breaks must not be used. Delete them.
  27: h4, h5, h6 should not be used. Use h1, h2 or h3.

credits.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead

finding-elements.cn.md
  2: h1 must not use === underline syntax. Use # instead
  21: h2 must not use --- underline syntax. Use ## instead
  145: h2 must not use --- underline syntax. Use ## instead

gestures.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead

grid.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead

grunt.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead
  31: h2 must not use --- underline syntax. Use ## instead

hybrid.cn.md
  2: h1 must not use === underline syntax. Use # instead
  10: h2 must not use --- underline syntax. Use ## instead
  145: h4, h5, h6 should not be used. Use h1, h2 or h3.
  151: h2 must not use --- underline syntax. Use ## instead

ios-deploy.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead

mobile-web.cn.md
  2: h1 must not use === underline syntax. Use # instead
  28: h4, h5, h6 should not be used. Use h1, h2 or h3.
  62: h4, h5, h6 should not be used. Use h1, h2 or h3.
  66: h4, h5, h6 should not be used. Use h1, h2 or h3.

mobile_methods.cn.md
  1: h1 is missing,h4, h5, h6 should not be used. Use h1, h2 or h3.
  3: h4, h5, h6 should not be used. Use h1, h2 or h3.
  19: h4, h5, h6 should not be used. Use h1, h2 or h3.
  21: h4, h5, h6 should not be used. Use h1, h2 or h3.
  45: h4, h5, h6 should not be used. Use h1, h2 or h3.

real-devices.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead
  16: h2 must not use --- underline syntax. Use ## instead
  24: h2 must not use --- underline syntax. Use ## instead
  35: h2 must not use --- underline syntax. Use ## instead

running-on-linux.cn.md
  2: h1 must not use === underline syntax. Use # instead
  8: each doc must contain exactly one h1
  20: each doc must contain exactly one h1
  29: each doc must contain exactly one h1

running-on-osx.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead
  6: h2 must not use --- underline syntax. Use ## instead
  13: h2 must not use --- underline syntax. Use ## instead
  27: h2 must not use --- underline syntax. Use ## instead

running-on-windows.cn.md
  2: h1 must not use === underline syntax. Use # instead
  10: each doc must contain exactly one h1
  30: each doc must contain exactly one h1
  37: each doc must contain exactly one h1
  44: each doc must contain exactly one h1
  48: each doc must contain exactly one h1
  54: each doc must contain exactly one h1
  57: each doc must contain exactly one h1

running-tests.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead
  5: h2 must not use --- underline syntax. Use ## instead
  15: h2 must not use --- underline syntax. Use ## instead
  19: h2 must not use --- underline syntax. Use ## instead
  47: h2 must not use --- underline syntax. Use ## instead
  85: h2 must not use --- underline syntax. Use ## instead

server-args.cn.md
  1: h1 is missing
  2: h1 must not use === underline syntax. Use # instead

troubleshooting.cn.md
  1: h1 is missing
  3: h1 must not use === underline syntax. Use # instead

how-to-write-docs.md
  17: h4, h5, h6 should not be used. Use h1, h2 or h3.

real-devices.md
  46: each doc must contain exactly one h1
```