Mark packages as stable by removing preview build tag (#13)

Remove -preview

Author: jeffkl

version.json

@@ -1,7 +1,8 @@
 {
   "$schema": "https://raw.githubusercontent.com/AArnott/Nerdbank.GitVersioning/master/src/NerdBank.GitVersioning/version.schema.json",
-  "version": "1.0-preview",
+  "version": "1.0",
   "assemblyVersion": "1.0",
+  "buildNumberOffset": -1,
   "nugetPackageVersion": {
     "semVer": "2",
     "precision": "minor"