Add 0.20.0 changes to CHANGELOG.md #5603

Job	Run time
build_windows (3.9)	55m 45s
build_linux (3.9)	36m 45s
build_windows (3.10)	56m 47s
build_windows (3.11)	57m 50s
build_windows (3.12)	57m 44s
build_windows (3.13)	56m 3s
build_linux (3.10)	36m 14s
build_linux (3.11)	36m 22s
build_linux (3.12)	37m 11s
build_linux (3.13)	37m 39s
array-api-conformity (3.10, false, ubuntu-22.04)	5m 10s
test_examples_linux (3.11, false, ubuntu-22.04)	7m 34s
test_linux (3.9, false, ubuntu-22.04)	10m 50s
test_linux (3.10, false, ubuntu-22.04)	10m 47s
test_linux (3.11, false, ubuntu-22.04)	10m 37s
test_linux (3.12, false, ubuntu-22.04)	10m 38s
test_linux (3.13, false, ubuntu-22.04)	10m 33s
upload_linux	0s
test_windows (3.9, false, windows-2019)	13m 26s
test_windows (3.10, false, windows-2019)	13m 4s
test_windows (3.11, false, windows-2019)	13m 12s
test_windows (3.12, false, windows-2019)	12m 59s
test_windows (3.13, false, windows-2019)	13m 4s
upload_windows	0s
Clean up anaconda packages	0s
	10h 0m 14s

Provide feedback