Fix image src links in pages downloaded by wayback machine

1. The problem

Some image links are full links to the original site image, when you download html from wayback.

Wayback page:

eg:

<img width="260" height="192" src="https://montagnesauvage.com/wp-content/uploads/2020/02/new-logo-2020.jpg" class="site-logo attachment-dyad-site-logo" alt="" data-size="dyad-site-logo" itemprop="logo" decoding="async" />

However, wayback processes these links to point to wayback archive image

src="https://web.archive.org/web/20210126112510im_/http://montagnesauvage.com/wp-content/uploads/2017/02/accueil-1024x311.jpg"

3. Screenshot examples

Page loads with imageon wayback

Fails on local copy