WIP: feat: add `update-backlog` subcmd. #193

Job	Run time
cargo-deny	1m 49s
Check (ubuntu-latest, stable)	36s
Check (ubuntu-latest, beta)	45s
Clippy (stable)	42s
Check (windows-latest, stable)	1m 14s
Clippy (beta)	44s
Check (windows-latest, beta)	1m 51s
Check (macOS-latest, stable)	42s
Rustfmt (stable)	7s
Check (macOS-latest, beta)	57s
Test Suite (ubuntu-latest, stable)	51s
Test Suite (ubuntu-latest, beta)	51s
Test Suite (windows-latest, stable)	31s
Test Suite (windows-latest, beta)	44s
Test Suite (macOS-latest, stable)	22s
Test Suite (macOS-latest, beta)	31s
	13m 17s

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