feat: add benchmark example

[louise-poole]

Sample output:

========== Benchmark Results on 100 swaps ==========

balancer_v2 - Mean Time: 733662.92 ns, Trimmed Mean Time: 691404.57 ns, Max Time: 2006833 ns, Min Time: 543667 ns, Std Dev: 197524.23 ns

Histogram:
  543667 - 689983   | ******************************************************
  689984 - 836300   | ********************************
  836301 - 982617   | ********
  982618 - 1128934  | **
 1128935 - 1275251  | *
 1275252 - 1421568  | *
 1421569 - 1567885  | *
 1567886 - 1714202  | 
 1714203 - 1860519  | 
 1860520 - 2006836  | *

---------------------------------------

curve - Mean Time: 1049883.33 ns, Trimmed Mean Time: 1049883.33 ns, Max Time: 3139791 ns, Min Time: 195916 ns, Std Dev: 694054.37 ns

Histogram:
  195916 - 490303   | *******************************
  490304 - 784691   | ********
  784692 - 1079079  | *******
 1079080 - 1373467  | **********************
 1373468 - 1667855  | ***************
 1667856 - 1962243  | ********
 1962244 - 2256631  | ****
 2256632 - 2551019  | **
 2551020 - 2845407  | *
 2845408 - 3139795  | **

---------------------------------------

uniswap_v2 - Mean Time: 872.96 ns, Trimmed Mean Time: 788.16 ns, Max Time: 4333 ns, Min Time: 625 ns, Std Dev: 434.01 ns

Histogram:
     625 - 995      | *********************************************************************************************
     996 - 1366     | ***
    1367 - 1737     | *
    1738 - 2108     | 
    2109 - 2479     | *
    2480 - 2850     | *
    2851 - 3221     | 
    3222 - 3592     | 
    3593 - 3963     | 
    3964 - 4334     | *

---------------------------------------

uniswap_v3 - Mean Time: 3976.23 ns, Trimmed Mean Time: 2223.01 ns, Max Time: 37416 ns, Min Time: 375 ns, Std Dev: 6028.50 ns

Histogram:
     375 - 4079     | ***************************************************************************************
    4080 - 7784     | ****
    7785 - 11489    | ***
   11490 - 15194    | 
   15195 - 18899    | *
   18900 - 22604    | 
   22605 - 26309    | ***
   26310 - 30014    | 
   30015 - 33719    | *
   33720 - 37424    | *

---------------------------------------

[dianacarvalho1]

Thank you @louise-poole ! 🙏🏼 Only have small comments, the rest looks really good!
Do you want me to run this as well to compare with your results?