🔖 set version to 3.8.0

doc/examples/README.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/uDkr2VTjsrssiXq3"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/EezQxM0Nzi8tTUEe"><b>online</b></a>

doc/examples/meta.output

@@ -10,8 +10,8 @@
     "url": "https://github.com/nlohmann/json",
     "version": {
         "major": 3,
-        "minor": 7,
-        "patch": 3,
-        "string": "3.7.3"
+        "minor": 8,
+        "patch": 0,
+        "string": "3.8.0"
     }
 }