Set release date for v0.13.0

AndreyAkinshin · AndreyAkinshin · commit 5c8469124736 · 2021-05-19T18:21:11.000+03:00
diff --git a/docs/_changelog/footer/v0.13.0.md b/docs/_changelog/footer/v0.13.0.md
@@ -1,4 +1,4 @@
-_Date: TBA_
+_Date: May 19, 2021_
 
 _Milestone: [v0.13.0](https://github.com/dotnet/BenchmarkDotNet/issues?q=milestone%3Av0.13.0)_
 ([List of commits](https://github.com/dotnet/BenchmarkDotNet/compare/v0.12.1...v0.13.0))

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-_Date: TBA_`
	`1`	`+_Date: May 19, 2021_`
`2`	`2`
`3`	`3`	`_Milestone: [v0.13.0](https://github.com/dotnet/BenchmarkDotNet/issues?q=milestone%3Av0.13.0)_`
`4`	`4`	`([List of commits](https://github.com/dotnet/BenchmarkDotNet/compare/v0.12.1...v0.13.0))`