Move BASE_URL to the build script

.vscode/tasks.json

@@ -21,7 +21,8 @@
         "cwd": "${workspaceFolder}/src/MistoxWebsite.Client"
       },
       "args": [
-        "build"
+        "build",
+        "--base-href=http://localhost:5000"
       ],
       "problemMatcher": "$msCompile"
     },