new iOS/web extractors, image proxying done by views.py

- ythdd_globals.py - added helper function to get user-configured header
- ythdd.py - now checks for config.toml in work directory
- requirements.txt - add brotli, so that requests can decompress
innertube request

config.default.toml

@@ -1,15 +1,19 @@
 [general]
-db_file_path = "/path/to/ythdd_db.sqlite" # Preferably stored on an SSD.
-video_storage_directory_path = "/path/to/videos/" # Path to video vault.
-is_proxied = false
+db_file_path = "/path/to/ythdd_db.sqlite"          # Preferably stored on an SSD.
+video_storage_directory_path = "/path/to/videos/"  # Path to video vault.
+is_proxied = false                                 # Set to true if running behind reverse proxy.
+public_facing_url = "http://localhost:5000/"       # Used for URL rewriting. Note the trailing backslash /.
 
 [api]
 api_key = "" # Leave empty API key for public access to non-sensitive backend
 api_key_admin = "CHANGEME" # Empty *admin* API key will autogenerate a random one every launch.
 
 [extractor]
-user-agent = "" # leave empty for default
-cookies_path = "" # leave empty for none
+user-agent = ""   # Leave empty for default (Firefox ESR).
+cookies_path = "" # Leave empty for none.
+
+[proxy]
+user-agent = ""   # Leave empty for default (Firefox ESR).
 
 [admin]
 # List of users with admin priviledges.