examples/flask_server: support loading parameters from file

examples/default.json

@@ -0,0 +1,28 @@
+{
+    "html_title": "500: Internal server error",
+    "title": "Internal server error",
+    "error_code": 500,
+    "more_information": {
+        "hidden": false,
+        "text": "cloudflare.com",
+        "link": "https://youtube.com/watch?v=dQw4w9WgXcQ"
+    },
+    "browser_status": {
+        "status": "ok"
+    },
+    "cloudflare_status": {
+        "status": "error",
+        "status_text": "Not Working"
+    },
+    "host_status": {
+        "status": "ok",
+        "location": "example.com"
+    },
+    "error_source": "cloudflare",
+    "what_happened": "<p>There is an internal server error on Cloudflare\"s network.</p>",
+    "what_can_i_do": "<p>Please try again in a few minutes.</p>",
+    "perf_sec_by": {
+        "text": "Cloudflare",
+        "link": "https://youtube.com/watch?v=dQw4w9WgXcQ"
+    }
+}