Exercise on packing data in felt using bitwise

[tekkac]

Description

Felts can be used to pack multiple pieces of data more efficiently.
Show how to can encode and decode multiple variables in a felt using bitwise operations and bit masking.

Resource:

• https://www.cairo-lang.org/docs/reference/common_library.html#common-library-bitwise
• https://perama-v.github.io/cairo/background/integer_lift/

Acceptance criteria

• Add a bitwise exercise on data packing
• The contract compiles and tests pass
• An exercise patch is generated