Update README.md with a important information about the app factory u…

[edipoferreira]

Took some time and testing to got this and one only after some testing found that is needed export the variable DEBUG_METRICS, this is a update suggestion on the README to help other if they found the same issue when testing the export using App Fabric Pattern.

Bellow the specific log message, only showed for me after make some specific testings and comparing results, outputs, maybe a enhacement on the future is make this message more clear when using the function for_app_factory()

 * Detected change in '//flask_hello_world/examples/flask_test_prometheus.py', reloading
 * Restarting with stat
[2024-04-20 11:08:01,540] DEBUG in __init__: Metrics are disabled when run in the Flask development server with reload enabled. Set the environment variable DEBUG_METRICS=1 to enable them anyway.
 * Debugger is active!
 * Debugger PIN: 325-243-250

[rycus86]

Hello,

It's unclear to me if this is new information compared to https://github.com/rycus86/prometheus_flask_exporter?tab=readme-ov-file#debug-mode ?

[edipoferreira]

Hello,

It's unclear to me if this is new information compared to https://github.com/rycus86/prometheus_flask_exporter?tab=readme-ov-file#debug-mode ?

Hello Rycus86, after I submitted the pull and was looking for other thing I saw this section. Not sure if this will make more clear to others.