update loglevel to str env var

README.md

@@ -22,9 +22,19 @@ Then just run the binary which you can compile yourself, download from `Releases
 
 ### Logging
 
-Set the log level with environment variable `Q3RCON_LOGLEVEL`:
+Set the log level with environment variable `Q3RCON_LOGLEVEL`.
 
-`0 = Panic, 1 = Fatal, 2 = Error, 3 = Warning, 4 = Info, 5 = Debug, 6 = Trace`
+Acceptable values are:
+
+- `trace`
+- `debug`
+- `info`
+- `warn`
+- `error`
+- `fatal`
+- `panic`
+
+If not set it will default to `info`.
 
 ### Special Thanks