Feat BitArray adds data structure for read/writing unary bits and enc…

…oding words in big/little endian notation (#191)

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## Pull Request type

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Please check the type of change your PR introduces:

- [ ] Bugfix
- [x] Feature
- [ ] Code style update (formatting, renaming)
- [ ] Refactoring (no functional changes, no API changes)
- [ ] Build-related changes
- [ ] Documentation content changes
- [ ] Other (please describe):

## What is the current behavior?

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Issue Number: N/A

## What is the new behavior?

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- Adds a BitArray that can read/write unary bits as well as words of all
sizes
- Supports encoding/decoding words in both big and little endian
- Packs bits within a bytes31 array
- Serialization and deserialization through Serde

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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Co-authored-by: Lucas @ StarkWare <[email protected]>