CompatHelper: bump compat for DocStringExtensions to 0.9, (keep exist…

…ing compat) (#418)

This pull request changes the compat entry for the `DocStringExtensions` package from `0.8` to `0.8, 0.9`.
This keeps the compat entries for earlier versions.



Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

Project.toml

@@ -26,7 +26,7 @@ Bijectors = "0.5.2, 0.6, 0.7, 0.8, 0.9, 0.10"
 ChainRulesCore = "0.9.7, 0.10, 1"
 ConstructionBase = "1"
 Distributions = "0.23.8, 0.24, 0.25"
-DocStringExtensions = "0.8"
+DocStringExtensions = "0.8, 0.9"
 MacroTools = "0.5.6"
 Setfield = "0.7.1, 0.8"
 ZygoteRules = "0.2"