calculateNumWords gas optimization

[michaelkaplan13]

Why this should be merged

• Fixes typo in README
• Optimizes calculateNumWords implementation to use less gas

Thanks to @bernard-avalabs for both of these suggestions here.

How this works

Uses bit shifting rather than division and mod.

How this was tested

Existing unit tests with forge test --gas-report

| Function Name                          | min             | avg   | median | max    | # calls |
| calculateNumWords (pre-update)         | 557             | 594   | 622    | 622    | 7       |
| calculateNumWords (post-update)        | 496             | 496   | 496    | 496    | 7       |

How is this documented

N/A

[openzeppelin-code[bot]]

calculateNumWords gas optimization

Generated at commit: 23ae996b23d7f9a01a4a10ca70bce42764ad1764

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	1 0 0 2 13 16
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

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