Use WiFiManager instead of hard wired AP user/password

[buttim]

This is easy and would even allow binary distribution of the firmware (no need for Arduino IDE installation and recompilation).

I gave it a try and it should be enough to do the following modifications to DIY_CameraSlider.ino_:

1. Replace #include "config_wifi.h" with #include <WiFiManager.h>
2. Add the declaration WiFiManager wifiManager; after all the includes
3. Remove the whole while after the comment // Connect to WiFi
4. Add in its place the single line wifiManager.autoConnect("DIY_CameraSlider", "cameraslider");

The file config_wifi.h can then be removed

[getsetbro]

I just tried this and I get conflicts due to WiFiManager.h and ESPAsyncWebServer.h both having HTTPMethods.