fixup! Add Xgram swap support

Author: j0ntz

src/swap/central/xgram.ts

@@ -6,6 +6,7 @@ import {
   asMaybe,
   asNumber,
   asObject,
+  asOptional,
   asString,
   asValue
 } from 'cleaners'
@@ -349,12 +350,12 @@ const asXgramError = asObject({
   )
 })
 const asXgramQuote = asObject({
-  ccyAmountToExpected: asNumber,
+  ccyAmountToExpected: asEither(asNumber, asString),
   depositAddress: asString,
   depositTag: asOptionalBlank(asString),
   id: asString,
   result: asBoolean,
-  expiresAt: asDate,
+  expiresAt: asOptional(asDate),
   ccyAmountFrom: asString
 })
 const asXgramQuoteReply = asEither(asXgramQuote, asXgramError)