Update changelog list

Halogen `requestAll` re-export. (#761)

Co-authored-by: Philippe Pittoli <karchnu@karchnu.fr>

Delete PULL_REQUEST_TEMPLATE.md

Update mdbook to v0.4.5 (#725)

Addresses https://blog.rust-lang.org/2021/01/04/mdbook-security-advisory.html

Fix typo in 04-Lifecycles-Subscriptions.md (#699)

Read most recent driver state when disposing (#676)

Fix markup of documentation comment (#663)