Add odysee support.

Currently, the LBRY support is limited to odysee.
This is because I only know of that instance.

scripts/determine_site.py

@@ -16,6 +16,8 @@ supported_sites = {
 
 	"github" : ["github.com"],
 
+	"lbry" : ["odysee.com"],
+
 	"player_fm" : ["player.fm/series/"],
 
 	"pocketcasts" : ["pca.st"],

scripts/extractors/lbry.py

@@ -0,0 +1,31 @@
+#!/usr/bin/python3
+
+from utils import *
+from download_page import download
+
+# portable code to get filename
+import os
+platform = os.path.basename(__file__)
+if platform.endswith(".py"):
+	platform = platform[:(-3)]
+
+def extract_from_url (url, verbosity):
+    # split into domain and path
+    index = url.find("/",url.find("//")+2)
+    domain = url[:index]
+    path = url[index:]
+
+    # get username
+    index = path.find("/",2)
+    if index > -1:
+        username = username = path[1:index]
+    else:
+        username = path[1:]
+
+    if len(username) > 0 and username[0] == "@":
+        return domain + "/$/rss/" + username
+
+def extract (url, page=None, network=False, verbosity=3, args={}):
+	feed = extract_from_url (url, verbosity)
+	if not feed is None:
+		return feed

tests/lbry.txt

@@ -0,0 +1,13 @@
+# channel page
+https://odysee.com/@techlore:3 https://odysee.com/$/rss/@techlore:3
+https://odysee.com/@Coldfusion:f https://odysee.com/$/rss/@Coldfusion:f
+
+# video page
+https://odysee.com/@techlore:3/the-dark-side-of-discord-(and-best:5 https://odysee.com/$/rss/@techlore:3
+https://odysee.com/@Coldfusion:f/exploring-ai-generated-music:f https://odysee.com/$/rss/@Coldfusion:f
+
+# TODO: playlist pages
+# note: While odysee has a "playlists" tab for channels, I didn't see any
+# evidence (on 2021-09-22) that playlists are an actual thing that exists.
+# If/when they get fully implemented and/or people start using them, I'll
+# have to add them.