Add themes `weeping-willow`, `mirthful-willow` #2243

Job	Run time
Clippy	47s
Rustfmt	12s
Integration tests (macos-latest)	2m 14s
Code coverage	2m 55s
Integration tests (ubuntu-latest)	2m 19s
Unit tests (macos-latest, aarch64-apple-darwin, false)	2m 7s
Unit tests (macos-12, x86_64-apple-darwin, false)	3m 10s
Unit tests (windows-latest, x86_64-pc-windows-msvc, false)	5m 35s
Unit tests (ubuntu-latest, x86_64-unknown-linux-gnu, false)	2m 22s
Unit tests (ubuntu-latest, x86_64-unknown-linux-musl, true)	3m 2s
Unit tests (ubuntu-latest, i686-unknown-linux-gnu, true)	2m 44s
Unit tests (ubuntu-latest, arm-unknown-linux-gnueabihf, true)	3m 2s
Unit tests (ubuntu-latest, aarch64-unknown-linux-gnu, true)	2m 56s
	33m 25s

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