Enhanced SimpleXML benchmarks

[kanevbg]

Continuation of #16 and thanks for adding :)

We should add operations with the extension else it is not really useful in practice.

Later I will comment suggested operations to do.

[sergey-dryabzhinsky]

Maybe we need to parse something big and complex?
Like unzipped OpenDocument/OpenXML xml file with alot of styles and etc.
Something free-to-distribute.
And try to search something, summarize and calculate something simple.

[kanevbg]

Yes, these basic operations seems great. Random data generation tool can be used to generate XML string/file for benchmarking purposes, eg I generated example file with that web tool: https://onlinerandomtools.com/generate-random-xml
output-onlinerandomtools.txt