Add TimeMap in the comparison table

[laeti-tia]

We regularly have users comment on the usefulness of perfSONAR if TimeMap is deployed in the network. It would be useful to clarify the differences between the 2 tools in our comparison table at https://www.perfsonar.net/gtk_comparison.html

TimeMap is described at https://network.geant.org/timemap/

Some differences that should be highlighted are:

• TimeMap is for the core network, measuring on network segments only, whereas perfSONAR is for the end-to-end measurements
• TimeMap is only doing latency and jitter measurements, perfSONAR metrics cover a more comprehensive range of network characteristics
• TimeMap automatically analyses the measurements to spot deviations, perfSONAR data analysis must be done externally
• TimeMap aims at giving helpful information for time-sensitive applications whereas perfSONAR is most useful for data-intensive applications
• TimeMap is meant to be used by network operators, perfSONAR is used by both network operators and end users
• TimeMap is restricted to a single network, perfSONAR operates across networks in a multi-domain setting.