[index] Improve error message for data transformation

Replace error message and add additional information:
- Name of the bridge
- Possible solutions
- Error description
- Error code
- Error message

The error description also includes an URI to create a new issue
on GitHub based on the given error information (prepared).

index.php

@@ -177,7 +177,32 @@ try {
 			$format->setExtraInfos($bridge->getExtraInfos());
 			$format->display();
 		} catch(Exception $e){
-			echo "The bridge has crashed. You should report this to the bridges maintainer";
+			$title = urlencode($bridge->getName() . ' failed with error ' . $e->getCode());
+			$body = urlencode('Error message: ' . $e->getmessage());
+			$link = 'https://github.com/rss-bridge/rss-bridge/issues/new?title='
+			. $title
+			. '&body='
+			. $body
+			. '&labels=bug+report'
+			. '&assignee='
+			. $bridge->getMaintainer();
+
+			$message = <<<EOD
+{$bridge->getName()} was unable to receive or process the remote website's content.
+Check your input parameters or press F5 to retry.
+
+Use the following link to notify the bridge maintainer if this error persists:
+$link
+
+Additional info:
+
+Error code: "{$e->getCode()}"
+Message: "{$e->getMessage()}"
+EOD;
+
+			header('HTTP/1.1 ' . $e->getCode() . ' ' . Http::getMessageForCode($e->getCode()));
+			header('Content-Type: text/plain');
+			die($message);
 		}
 		die;
 	}