Add release notes for v0.2.8 #23

Job	Run time
Build submodules (ARM64)	1m 4s
Build submodules (x64)	1m 1s
Build NaturalVoiceSAPIAdapter (x86)	2m 43s
Build submodules (x86)	1m 11s
Build NaturalVoiceSAPIAdapter (ARM64)	3m 10s
Build NaturalVoiceSAPIAdapter (x64)	1m 58s
release	26s
	11m 33s

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