Add layout option and style

[mdubus]

What's wrong ?

Problem 1:

docs-searchbar provides an option to choose between 2 layouts : "simple" and "columns". But the plugin vuepress-plugin-meilisearch doesn't provide access to this existing option.

Problem 2:

After making this option available, the design looks horrific:

What's inside this PR

This PR makes the layout option available. It also adapts the style to match the existing one in docs-searchbar.

Style in docs-searchbar (simple layout):

Style in vuepress-plugin-meilisearch after this PR (simple layout):

How to test

Go to the file playground/.vuepress/config.js and add "layout": "simple" in the options:

Note that you might need to restart your server.

Please make sure to test that it doesn't break the "columns" layout 🙏

[bidoubiwa]

bors merge

[bidoubiwa]

bors merge

[bidoubiwa]

bors merge

[bors[bot]]

Build succeeded:

• linter-check
• tests