Bump version to 0.8.0, update CHANGELOG.md

[MaxDesiatov]

Almost a month has passed since the last release, it would be great to tag a new one. This would also make it easier using new stuff in libraries depending on JavaScriptKit.

[github-actions]

Time Change: -171.75ms (1%)

Total Time: 9,673.5ms

ℹ️ View Unchanged

Test name	Duration	Change
Serialization/Write JavaScript number directly	178ms	+2ms (1%)
Serialization/Write JavaScript string directly	180.5ms	-0.75ms
Serialization/Swift Int to JavaScript	3,191.75ms	-49.5ms (1%)
Serialization/Swift String to JavaScript	3,243.25ms	-39.25ms (1%)
Object heap/Increment and decrement RC	2,880ms	-84.25ms (2%)

_{performance-action}

[MaxDesiatov]

@kateinoigakukun would you mind if this is merged and released today?