[FEATURE] Manually input exchange rate on Income/Expense record

[tnnyx]

Please confirm the following:

• [X] I've checked the current issues for duplicate issues.
• [X] I've requested a single (only one) feature/change in this issue. It complies with the One Request Per GitHub Issue (ORPGI) rule.
• [X] My issue is well-defined and describes how it should be implemented from UI/UX perspective.

What do you want to be added or improved?

As a user I want to able to manually input the exchange rate per record/transaction. This feature request is available when making an Account Transfer record but can't be found when creating an Income/Expense record.

Why do you need it?

• It messes with the total calculation of my entire wallet/record. Although this can be remedied by excluding the foreign account, but I want it to include it, so I can have a full picture of my accounting.
• It gives user the ability to capture the current exchange rate when they made the transaction.

How do you imagine it?

• When creating an Income/Expense record, it should have the "Exchange Rate" at the bottom just like when making an "Account Transfer" record.

[ivywallet]

Thank you @tnnyx for raising Issue #3612! 🚀 What's next? Read our Contribution Guidelines 📚.

Tagging @ILIYANGERMANOV for review & approval 👀