Pronoun-related updates to people page

Two requested changes:

1. Add optional pronoun.is urls to people's contents.lr files and display them as clickable link. Pronoun island urls are non-trivial, so it would most likely be best to store the pronoun.is url and the existing pronoun string as separate things (rather than attempting to create a mapping).

2. Change PRO: string in people.html to appropriately styled 'pronoun:' string.