Add language & version meta for algolia docsearch

[endiliey]

Motivation

algolia/docsearch-configs#454 (comment)

In order to help algolia docsearch scrape our docs better, we will provide Docsearch metadata.
cc @s-pace

Changes

Provide docsearch metadata on head. Example:

<meta name="docsearch:version" content='1.2.1'>
<meta name="docsearch:language" content='en'>

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Before

After

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[JoelMarcey]

Thank you!

[stoffeastrom]

FYI

To get the new meta data I had to add

onPageNav: 'separate'

in the siteConfig.js

[endiliey]

@stoffeastrom do you have an example repo ?
I don't think it's true. I removed onPageNav: 'separate' and the meta is still there

[stoffeastrom]

Strange, I did the same and now it still adds them 🤔
When debugging it from the beginning the

this.props.version

was undefined in lib/core/Head.js

[endiliey]

Oh. that meta is only for docs by the way. Because there is no concept of version for home page :)

[stoffeastrom]

Yeah I know, I need it so Algolia starts indexing my next version :)

[endiliey]

Hmm .. It is hard for me to guess without understanding what you did 😂
But anyway I'll be glad to help if you encounter a problem