Bump to 0.21 #452

Job	Run time
Check documentation	47s
Formatter check	13s
Clippy check (ubuntu-latest)	48s
Clippy check (ubuntu-latest, manage_clipboard)	1m 8s
Clippy check (ubuntu-latest, open_url)	1m 9s
Clippy check (ubuntu-latest, manage_clipboard,open_url)	1m 0s
Clippy check (macos-latest)	1m 29s
Clippy check (macos-latest, manage_clipboard)	1m 9s
Clippy check (macos-latest, open_url)	59s
Clippy check (macos-latest, manage_clipboard,open_url)	58s
Clippy check (windows-latest)	3m 4s
Clippy check (windows-latest, manage_clipboard)	4m 47s
Clippy check (windows-latest, open_url)	4m 23s
Clippy check (windows-latest, manage_clipboard,open_url)	3m 21s
Clippy check (wasm32) (immutable_ctx)	35s
Clippy check (wasm32) (manage_clipboard)	35s
Clippy check (wasm32) (open_url)	35s
Clippy check (wasm32) (manage_clipboard,open_url)	34s
Run tests	5m 28s
	33m 2s

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