Add support for Revolut Crypto

[ccoles146]

Describe the converter
I was hoping that the Revolut converter would handle Crypto but it seems to only do stocks.

Provide example input

Completed Date;Reference;Paid Out (LTC);Paid In (LTC);Exchange Out;Exchange In; Balance (LTC);Exchange Rate;Category
16. Dec 2020;Sold LTC for EUR;7,5676 ;;EUR 559,34 ;;0,00007128 ;FX-rate 1 LTC = 74,0140 €, Fee=0,76 €;General
5. Aug 2020;Bought LTC with EUR;;0,99156503 ;;EUR 50,00 ;7,56767128 ;FX-rate 1 LTC = 50,4253 €;General
13. Jun 2018;Bought LTC with GBP;;6,57610625 ;;GBP 500,00 ;6,57610625 ;FX-rate 1 LTC = 76,0328 £;General

Here is another example where SGD are held, but then accidentally withdrawn. Would be helpful to track. This should be possible right?

Completed Date;Reference;Paid Out (SGD);Paid In (SGD);Exchange Out;Exchange In; Balance (SGD);Exchange Rate;Category
26. Nov 2020;Sold SGD for EUR;85,00 ;;EUR 53,30 ;;1,15 ;FX-rate 1 S$ = 0,6271 €;General
26. Nov 2020;From SGD savings;;70,00 ;;;86,15 ; ;Savings
21. Sep 2020;Amazon;24,18 ;;EUR 15,00 ;;16,15 ;FX-rate 1 S$ = 0,6205 €;General
1. Sep 2020;From Singapore savings;;40,00 ;;;40,33 ; ;Savings
28. Aug 2020;To Singapore savings;40,00 ;;;;0,33 ; ;Savings
26. Aug 2020;Lidl Hrvatska F200 Pul;64,39 ;;HRK 299,91 ;;40,33 ;FX-rate 1 S$ = 4,6578 HRK;Groceries
24. Aug 2020;To SGD savings;2.700,00 ;;;;104,72 ; ;Savings
24. Aug 2020;Cash at Titova Riva 15;93,25 ;;HRK 429,30 ;;2.804,72 ;FX-rate 1 S$ = 4,6039 HRK;Cash
24. Aug 2020;Pbz9plodine;105,91 ;;HRK 487,58 ;;2.897,97 ;FX-rate 1 S$ = 4,6039 HRK;Groceries
5. Aug 2020;Bought SGD with EUR;;194,30 ;;EUR 120,00 ;3.003,88 ;FX-rate 1 S$ = 0,6176 €;General
20. Jul 2020;Bought SGD with GBP;;1.744,30 ;;GBP 1.000,00 ;2.809,58 ;FX-rate 1 S$ = 0,5733 £;General
13. Mar 2020;Bought SGD with GBP;;524,99 ;;GBP 300,00 ;1.065,28 ;FX-rate 1 S$ = 0,5714 £;General
5. Feb 2020;Bought SGD with GBP;;540,29 ;;GBP 300,00 ;540,29 ;FX-rate 1 S$ = 0,5553 £;General

Additional context
I guess this is the same for most currency conversions for example XAU, XAG, etc. which can also be held in Revolut.

I'm just working out if it's even possible manually, but it seems it's not really set up to handle currency investments. There's probably a way to do it but I've not found it yet.

Thanks.