Update fmusim usage in readme

Author: t-sommer

README.md

@@ -15,17 +15,22 @@ Use the [fmusim](fmusim) executable to simulate an FMU:
 ```commandline
 > fmusim --help
 Usage: fmusim [OPTION]... [FMU]
-Simulate a Functional Mock-up Unit (FMU).
+Simulate a Functional Mock-up Unit and write the output to result.csv.
 
   --help                        display this help and exit
   --start-time [VALUE]          set the start time
   --stop-time [VALUE]           set the stop time
   --output-interval [VALUE]     set the output interval
   --start-value [name] [value]  set a start value
+  --output-variable [name]      record a specific variable
   --input-file [FILE]           read input from a CSV file
   --output-file [FILE]          write output to a CSV file
   --log-fmi-calls               log FMI calls
   --fmi-log-file [FILE]         set the FMI log file
+  --solver [euler|cvode]        the solver to use
+  --early-return-allowed        allow early return
+  --event-mode-used             use event mode
+  --record-intermediate-values  record outputs in intermediate update
 
 Example: