Add Go 1.15.0

[versions-manifest] Update for release from 08/12/2020

versions-manifest.json

@@ -1,4 +1,29 @@
 [
+  {
+    "version": "1.15.0",
+    "stable": true,
+    "release_url": "https://github.com/actions/go-versions/releases/tag/1.15.0-20200812.1",
+    "files": [
+      {
+        "filename": "go-1.15.0-darwin-x64.tar.gz",
+        "arch": "x64",
+        "platform": "darwin",
+        "download_url": "https://github.com/actions/go-versions/releases/download/1.15.0-20200812.1/go-1.15.0-darwin-x64.tar.gz"
+      },
+      {
+        "filename": "go-1.15.0-linux-x64.tar.gz",
+        "arch": "x64",
+        "platform": "linux",
+        "download_url": "https://github.com/actions/go-versions/releases/download/1.15.0-20200812.1/go-1.15.0-linux-x64.tar.gz"
+      },
+      {
+        "filename": "go-1.15.0-win32-x64.zip",
+        "arch": "x64",
+        "platform": "win32",
+        "download_url": "https://github.com/actions/go-versions/releases/download/1.15.0-20200812.1/go-1.15.0-win32-x64.zip"
+      }
+    ]
+  },
   {
     "version": "1.14.7",
     "stable": true,