Add `v1.6.0-alpha.1` changelog #5199

Job	Run time
check-for-run-condition	1s
check-for-modification	6s
build-wasm	0s
test-wasm	0s
test-wasm-firefox	0s
test-wasm-chrome	0s
build-and-test (ubuntu-24.04)	21m 35s
build-and-test (macos-latest)	14m 9s
build-and-test (windows-latest)	51m 50s
	1h 27m 41s

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