Style external links

[mhwelander]

With the usual 'external link' icon (maybe we have something on prisma.io?)

[nilubava]

Something like this for external links:

[nilubava]

Waiting for confirmation from Docs team

[nilubava]

@meletj to check with Doc writers for feedback

[meletj]

I'm going through these - there were a few pages where we need to update the content so it's not overwhelming with a long list of external links.

[nilubava]

@meletj to check Percy/LP again