[WIP] Book example with media

[ultrasaurus]

this fails with this error...

which also appears in the browser, when I do this

RUST_LOG=info cargo run -- --book -i examples/book-media/source/ -t examples/book-media/book-template
unzip book.epub -d epub
open epub/OEBPS/credits.xhtml

this is the line in question:

<li>Cover Image by <a href="https://pixabay.com/users/paligraficas-6638487/?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=4386221">Augusto Ordóñez</a> from <a href="https://pixabay.com//?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=4386221">Pixabay</a></li>

column 115 appears to be the = directly after utm_medium

[ultrasaurus]

initial commit caused failure with this error...

which also appears in the browser, when I do this

RUST_LOG=info cargo run -- --book -i examples/book-media/source/ -t examples/book-media/book-template
unzip book.epub -d epub
open epub/OEBPS/credits.xhtml

this is the line in question:

<li>Cover Image by <a href="https://pixabay.com/users/paligraficas-6638487/?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=4386221">Augusto Ordóñez</a> from <a href="https://pixabay.com//?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=4386221">Pixabay</a></li>

column 115 appears to be the = directly after utm_medium

[ultrasaurus]

ampersand is correctly escaped when link is implemented as pure markdown