docs: release notes for 1.5.1 (#7156) #14620

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	29m 22s
Gradle MacOS integration	11m 17s
windows-latest jdk-17 unit tests 2 / 2	29m 9s
Sbt integration	49m 4s
macOS-latest jdk-17 unit tests 1 / 2	53m 4s
Maven integration	9m 27s
macOS-latest jdk-17 unit tests 2 / 2	46m 55s
Gradle integration	9m 38s
ubuntu-latest jdk-17 unit tests 1 / 2	19m 51s
Scala CLI integration	14m 35s
ubuntu-latest jdk-17 unit tests 2 / 2	17m 16s
Mill integration	39m 59s
Bazel integration	11m 42s
LSP integration tests	35m 39s
Scala cross tests	36m 9s
Formatting	39s
Scalafix and docs	4m 34s
Sbt-metals/scripted jdk11	2m 50s
sbt-metals/scripted (Sbt 2)	1m 25s
Scala javapc tests	1m 44s
Scala 2.11 cross tests	4m 11s
MiMa	1m 0s
	7h 9m 30s

Provide feedback