Palette link in docs broken

[ghost]

• I confirm that this is an issue rather than a question.

[palette](../config/README.md#palette) in https://github.com/vuejs/vuepress/blame/master/packages/docs/docs/theme/writing-a-theme.md#L32 should be [palette](../config/README.md#palette-styl)

One would expect that the link to the not existing anchor tag took you to the top of the page but instead it scrolls down a bit. There is probably something else going wrong (maybe related to #1016).

[ulivz]

Thanks, updated at 2b40e7e