Display a summary of platform fees

[IsaacCheng9]

Summary

• Display a summary of the fees paid to each platform based on the user's current portfolio and transaction history.
• Information may include:
  • Total fees paid across the portfolio
  • Fees paid as a percentage of portfolio
  • Platform fee percentage
  • Total fees paid to each platform
  • Weighting of fees across portfolio
    • e.g. out of all fees, 75% went to Vanguard, 25% went to Freetrade

Prerequisite Issues

• #20