added local docfx installation

.config/dotnet-tools.json

@@ -0,0 +1,12 @@
+{
+  "version": 1,
+  "isRoot": false,
+  "tools": {
+    "docfx": {
+      "version": "2.61.0",
+      "commands": [
+        "docfx"
+      ]
+    }
+  }
+}

Jenkinsfile

@@ -18,7 +18,9 @@ pipeline {
         branch 'main'
       }
       steps {
-        sh 'cd docs; docfx'
+        sh '''cd docs
+              dotnet tool restore
+              dotnet docfx'''
         sh 'rm -rf /var/www/tinylifedocs/*'
         sh 'cp -r docs/_site/. /var/www/tinylifedocs/'
       }