ui: Refactor offers page / Added TOR <> API / Cache

Restructure / Refactor JS for the Offers page.
Added TOR for chart/rates/coin prices/ API requests.
New Chart with option of show volume(coin) / refresh chart (will clear cache).
Added cache (10min) for all the API's or manual refresh.
Disabled notifications show new offers (was spam). New bids and Bid Accepted still active.
Various small fixes.

basicswap/js_server.py

@@ -38,7 +38,6 @@ from .ui.util import (
 from .ui.page_offers import postNewOffer
 from .protocols.xmr_swap_1 import recoverNoScriptTxnWithKey, getChainBSplitKey
 
-
 def getFormData(post_string: str, is_json: bool):
     if post_string == '':
         raise ValueError('No post data')
@@ -763,7 +762,26 @@ def js_help(self, url_split, post_string, is_json) -> bytes:
     for k in pages:
         commands.append(k)
     return bytes(json.dumps({'commands': commands}), 'UTF-8')
-
+    
+def js_readurl(self, url_split, post_string, is_json) -> bytes:
+    swap_client = self.server.swap_client
+    post_data = {} if post_string == '' else getFormData(post_string, is_json)
+    if have_data_entry(post_data, 'url'):
+        url = get_data_entry(post_data, 'url')
+        default_headers = {
+            'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36',
+            'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
+            'Accept-Language': 'en-US,en;q=0.5',
+        }
+        response = swap_client.readURL(url, headers=default_headers)
+        try:
+            error = json.loads(response.decode())
+            if "Error" in error:
+                return json.dumps({"Error": error['Error']}).encode()
+        except json.JSONDecodeError:
+            pass
+        return response
+    raise ValueError('Requires URL.')
 
 pages = {
     'coins': js_coins,
@@ -789,9 +807,9 @@ pages = {
     'unlock': js_unlock,
     'lock': js_lock,
     'help': js_help,
+    'readurl': js_readurl,
 }
 
-
 def js_url_to_function(url_split):
     if len(url_split) > 2:
         return pages.get(url_split[2], js_404)