feat(eval): add markdown export for hit rates and average ages

- Introduced functionality to export hit rates and average ages as markdown files.
- Generated `hit_rates.md` and `avg_ages.md` for easier sharing and reporting.

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

experiments/avg_ages.md

@@ -0,0 +1,8 @@
+|    |   avg_ages |
+|---:|-----------:|
+|  0 |   0.240582 |
+|  1 |   0.491436 |
+|  2 |   1.00288  |
+|  3 |   1.48616  |
+|  4 |   1.99204  |
+|  5 |   2.45903  |

experiments/hit_rates.md

@@ -0,0 +1,8 @@
+|    |   hit_rates |
+|---:|------------:|
+|  0 |    0.45867  |
+|  1 |    0.613708 |
+|  2 |    0.751005 |
+|  3 |    0.815118 |
+|  4 |    0.852101 |
+|  5 |    0.87731  |