Add "Hello World" page to the root folder of BLE Extension

[ralphsiegert]

As a user and administrator, I want to see if the service I just installed is running that I can continue configuring the systems and reduce a non working service as error source.

Explanation:

I was installing BLE Extension on an external machine. To test I typed in the URL of the service. If you check the error message in detail, you'll see a 404 message. My improvement idea is a page delivered as default that contains the following message.

Message idea:

Hello World,
I am the BLE extension of TSC and it looks like I am running. Please configure everything on your TSC instance.
If you know what you are doing, you can access here /swagger/ .

Project Homepage & manuals: https://github.com/pkuehnel/TeslaSolarCharger

---

(In an extended version this page could also contain some debug information such the BLE device and if it is accessible, but this might be another feature request"