docs(2023): add note on performance increase day 8

rust/2023/README.md

@@ -50,4 +50,4 @@ With the help of [cargo-aoc](https://github.com/gobanos/cargo-aoc) I get automat
 |   3 | 172.23 µs |        - |    Baseline | [Link](https://github.com/believer/advent-of-code/blob/75a83e31024bbac99a0664f81fce4e13ec1e94af/rust/2023/src/day_03.rs) |
 |   4 |  24.33 µs | 24.32 µs |    Baseline | [Link](https://github.com/believer/advent-of-code/blob/c970c6322d3904048bcf3f30b1052e2916476d73/rust/2023/src/day_04.rs) |
 |   5 |   1.50 µs |  21.22 s |    Baseline | [Link](https://github.com/believer/advent-of-code/blob/39b0904c4921f4ae79963a6df49bb3502ef6b3be/rust/2023/src/day_05.rs) |
-|   8 |         - | 15.25 ms |    Baseline | [Link](https://github.com/believer/advent-of-code/blob/4b96f6e935734f657469b091072282f1c430bcd3/rust/2023/src/day_08.rs) |
+|   8 |         - | 15.25 ms |    Baseline | [Link](https://github.com/believer/advent-of-code/blob/912d70c6e04ffd97f766c79b90764c105fe2f6ce/rust/2023/src/day_08.rs) |

rust/2023/src/day_08.rs

@@ -12,6 +12,12 @@ use std::collections::HashMap;
 // it would just loop. This meant that we can calculate the steps for each
 // start location, and then find the least common multiple of all the steps.
 // The answer turned out to be _huge_, so no real way of brute forcing it.
+//
+// It turns out the when I refactored to using the Direction enum, I also gained
+// a huge performance boost. About 70% faster. I think it's because I could
+// change getting directions using chars().nth(index) to just directions.get(index)
+// in two places inside the loop. I didn't run the benchmarks after that change.
+// I had no idea that it would make that much of a difference.
 
 #[derive(Debug)]
 enum Direction {