Optimize code paths

This PR significantly increases the speed of encoding by optimizing blocklist checking, which were very expensive. It also adds a simple performance testing script. The performance improvements are made possible by pre-filtering the blocklist into groups: * Words that must be matched exactly (3 characters long) * Words that must be matched at the start or end of the ID (those containing numbers) * Words that can be matched anywhere in the ID This pre-filtering allows blocklist checks to eliminate almost all looping in Python. Here is the output of the performance testing for the `main` branch before this PR, and for this PR branch: ``` Before changes: After changes: $ python assets/performance.py $ python assets/performance.py Iterations: 100,000 Iterations: 100,000 Instantiate: 23.493 Instantiate: 1.447 Encode [0]: 2.245 Encode [0]: 0.211 Encode [0, 1, 2]: 18.278 Encode [0, 1, 2]: 2.798 Decode 'bM': 0.350 Decode 'bM': 0.366 Decode 'rSCtlB': 2.490 Decode 'rSCtlB': 2.621 ``` As you can see, IDs can be encoded ~85% faster. Although it's not reflected in these performance tests, if a non-default alphabet or blocklist is used, instantiation will require more up-front computation to filter the blocklist, but the encoding will still be faster. Decode times are not affected by these changes.