Add information about dumping of GrallVM IR graph in documentaiton

[andrii0lomakin]

Currently TornadoVM does not dump IR Graph when system properties such as -Djdk.graal.Dump, -Djdk.graal.DumpOnError and so on are provided.

Usage of such properties will allow the use of an Ideal Graph Visualizer (IGV) for the development of different Phases and tracking of bugs.

[andrii0lomakin]

It is a very simple change to implement and quite a handy tool for me, so I will do that if there are no objections.

[jjfumero]

We have tornado --igv YourProgram. We use it quite frequently. You need to have IGV open in background, and it will dump all intermediate compilation phases in IGV.

[andrii0lomakin]

Yeah, found it. Thank you. Works like a charm. Did not find it there https://tornadovm.readthedocs.io/en/latest/flags.html . Let me keep this issue. I will add changes in the documentation.

[andrii0lomakin]

@jjfumero JFYI, I am using https://github.com/Shopify/seafoam , it is less feature complete but is more usable IMHO.