fix(blog): apply baseUrl to relative image in blog authors

[OzakIOne]

Motivation

Fix #10434

Fix is kinda ugly, baseUrl things are a bit of a pain, moreover now we have 2 separate datas, the one from getAuthorsMap in loadContent and authorsMap in contentLoaded

Deprecating / removing inline authors would simplify things

Test Plan

unit tests

Test links

Deploy preview: https://deploy-preview-10440--docusaurus-2.netlify.app/