Added information about debugging

ISSUE_TEMPLATE.md

@@ -17,7 +17,21 @@ What happens instead?
 
 ### Logs
 
-Please use Gist (https://gist.github.com/) or a similar code paster for longer
-logs.
+Debug output is essential to identify the problem. You can enable debugging by
+editing the file `opensc.conf`:
+```
+    # A debug level of 3 catches most problems
+    # Some sensitive data may be logged, too, (e.g. PIN codes)
+    debug = 3;
 
-```Paste Log output with less than 10 lines here```
+    # Where to write the debug output (default: `stdout`)
+    #debug_file = opensc-debug.log
+```
+
+Please use Gist (https://gist.github.com/) or a similar code paster for longer
+logs. Before pasting here, remove your sensitive data from your log (e.g. PIN
+code or certificates).
+
+```
+Paste Log output with less than 10 lines here
+```