Add Optional Summary of File Types and their Count

[Speedrunyourknowledge]

Description

This PR resolves #8 and #9. This closes user story #3.

What this PR Does

When the user runs Magika in the CLI, they now have the option of providing a --summary flag.
If this flag is active (and the --json flag is not active), then Magika's normal output will be followed by a list of detected file types and their count.

Implementation

I updated the Rust source file rust/cli/src/main.rs to keep track of how many times each file type was detected.
I configured the summary list to display in order of descending file count, followed by alphabetical order. I also color coded each file type to match the colors in Magika's normal output.

To use the modified Rust file rather than the pre-packaged Rust binary, I ran cargo run <my_file> in the CLI instead of magika <my_file>.

How This Was Tested

From within the rust/cli directory, I ran cargo +nightly fmt -- --check to ensure my code syntactically matches the existing code. I also ran ./test.sh to ensure my code passes the unit tests.

Screenshots

Output of cargo run -- --recursive --summary ../../tests_data