Add Scala 2.13.8 to supported versions (#15)

* Add Scala 2.13.8 to cross versions
* Update CI to use 2.13.8

Author: WojciechMazur

.github/workflows/CI.yml

@@ -7,7 +7,7 @@ jobs:
       fail-fast: false
       matrix:
         OS: [ubuntu-18.04, windows-2019]
-        scala: [2.12.15, 2.13.7, 3.1.0]
+        scala: [2.12.15, 2.13.8, 3.1.0]
     steps:
       - uses: actions/checkout@v2
       - uses: olafurpg/setup-scala@v13

build.sbt

@@ -1,5 +1,5 @@
 val crossScalaVersions212 = (13 to 15).map(v => s"2.12.$v")
-val crossScalaVersions213 = (4 to 7).map(v => s"2.13.$v")
+val crossScalaVersions213 = (4 to 8).map(v => s"2.13.$v")
 val crossScalaVersions3 = Seq("3.1.0")
 val latestsScalaVersions =
   Seq(crossScalaVersions212, crossScalaVersions213, crossScalaVersions3).map(