Added dotnet tools

Source/.config/dotnet-tools.json

@@ -0,0 +1,12 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "dotnet-stryker": {
+      "version": "3.11.1",
+      "commands": [
+        "dotnet-stryker"
+      ]
+    }
+  }
+}

Source/.config/stryker-config.json

@@ -0,0 +1,15 @@
+{
+  "stryker-config":
+  {
+    "solution": "../QuestPDF.sln",
+    "project": "QuestPDF/QuestPDF.csproj",
+    "test-projects": ["../QuestPDF.LayoutTests/QuestPDF.LayoutTests.csproj"],
+    "mutate": ["**/*Column.cs"],
+    "reporters": [
+      "progress",
+      "html"
+    ],
+    "disable-mix-mutants": true,
+    "disable-bail": true
+  }
+}