Benchmark images are not displayed

[homersimpsons]

Navigate to https://rustpython.github.io/benchmarks.

Notice that the first images are not displayed:

This is because those are cbor files, at the bottom we can see the actual svg files.

This is certainly because we are not correclt loading them in https://github.com/RustPython/rustpython.github.io/blob/master/_layouts/benchmarks.html

In fact the data/main folder should not be loaded (directories with cbor files): https://github.com/RustPython/rustpython.github.io/tree/master/assets/criterion/data/main

But the root one should be (directories with svg files): https://github.com/RustPython/rustpython.github.io/tree/master/assets/criterion

I wanted to tackle this issue but came across #65