Add support for 2.12.15 (#370)

* Add support for 2.12.15

* Bump version of scalameta to 4.4.28

Author: ckipp01

Diff for: .github/workflows/ci.yml

@@ -19,6 +19,7 @@ jobs:
         java: [ '8', '11' ]
         scala: [
             { version: '2.11.12' },
+            { version: '2.12.15' },
             { version: '2.12.14' },
             { version: '2.12.13' },
             { version: '2.12.12' },

Diff for: bin/test-release.sh

@@ -12,6 +12,7 @@ coursier fetch \
   org.scoverage:scalac-scoverage-plugin_2.12.12:$version \
   org.scoverage:scalac-scoverage-plugin_2.12.13:$version \
   org.scoverage:scalac-scoverage-plugin_2.12.14:$version \
+  org.scoverage:scalac-scoverage-plugin_2.12.15:$version \
   org.scoverage:scalac-scoverage-plugin_2.13.0:$version \
   org.scoverage:scalac-scoverage-plugin_2.13.1:$version \
   org.scoverage:scalac-scoverage-plugin_2.13.2:$version \

Diff for: build.sbt

@@ -2,11 +2,20 @@ import sbtcrossproject.CrossProject
 import sbtcrossproject.CrossType
 
 val scalatestVersion = "3.2.9"
-val scalametaVersion = "4.4.20"
+val scalametaVersion = "4.4.28"
 val defaultScala213 = "2.13.6"
 val bin211 = Seq("2.11.12")
 val bin212 =
-  Seq("2.12.14", "2.12.13", "2.12.12", "2.12.11", "2.12.10", "2.12.9", "2.12.8")
+  Seq(
+    "2.12.15",
+    "2.12.14",
+    "2.12.13",
+    "2.12.12",
+    "2.12.11",
+    "2.12.10",
+    "2.12.9",
+    "2.12.8"
+  )
 val bin213 =
   Seq(
     defaultScala213,