Add source description and source_url.

src/pricehist/cli.py

@@ -24,6 +24,8 @@ def cmd_source(args):
     source = sources.by_id[args.identifier]
     print(f'ID          : {source.id()}')
     print(f'Name        : {source.name()}')
+    print(f'Description : {source.description()}')
+    print(f'URL         : {source.source_url()}')
     pass
 
 def build_parser():

src/pricehist/sources/CoinMarketCap.py

@@ -6,4 +6,14 @@ class CoinMarketCap():
 
     @staticmethod
     def name():
-        return 'CoinMarketCap.com'
+        return 'CoinMarketCap'
+
+    @staticmethod
+    def description():
+        return 'CoinMarketCap historical price data'
+
+    @staticmethod
+    def source_url():
+        return 'https://coinmarketcap.com/'
+
+

src/pricehist/sources/ECB.py

@@ -8,3 +8,10 @@ class ECB():
     def name():
         return 'European Central Bank'
 
+    @staticmethod
+    def description():
+        return 'European Central Bank Euro foreign exchange reference rates'
+
+    @staticmethod
+    def source_url():
+        return 'https://www.ecb.europa.eu/stats/exchange/eurofxref/html/index.en.html'