Add Warning for High Impact Swaps.

[odesium]

Add a warning for users to confirm if the swap has a high impact before actual execution.

Many new users are not aware of what this means and whether they will suffer a loss until the swap is actually executed.

[suspi]

I second this. The *swap platforms disallows swaps with 15%+ price impacts.

And it gives a big warning if it's higher than 5%.