WIP: feat: add `update-backlog` subcmd. #240

Job	Run time
cargo-deny	20s
Rustfmt (stable)	11s
Clippy (stable)	34s
Clippy (beta)	36s
Check (ubuntu-latest, stable)	33s
Test Suite (ubuntu-latest, stable)	45s
Check (ubuntu-latest, beta)	35s
Test Suite (ubuntu-latest, beta)	44s
Check (windows-latest, stable)	37s
Check (windows-latest, beta)	38s
Test Suite (windows-latest, stable)	45s
Check (macOS-latest, stable)	34s
Test Suite (windows-latest, beta)	49s
Test Suite (macOS-latest, stable)	45s
Check (macOS-latest, beta)	37s
Test Suite (macOS-latest, beta)	44s
	9m 47s

Provide feedback