[Feat][C++][Doc] Add the documentation and tutorials about Filter Pushdown of C++ Reader

[lixueclaire]

Is your feature request related to a problem? Please describe. Currently, the C++ Reader has already supported Filter Pushdown, we can add a page in the documentation and use some examples/tutorials to introduce this feature.

Describe the solution you'd like Add examples in the "cpp/examples" directory, and add the documentation under "USER GUIDE".

Additional context related to #98 and #168