Add support: SBTV.com (local news livestreams)

[allai]

Checklist

• I'm reporting a new site support request
• I've verified that I'm running youtube-dl version 2020.06.16.1
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that none of provided URLs violate any copyrights
• I've searched the bugtracker for similar site support requests including closed ones

Example URLs

• Single video: https://www.sbtv.com/live/11937/wfmz

Description

Please consider adding support for SBTV.com, which hosts many free live streams for American local news affiliates. No credentials are needed.

youtube-dl --verbose 'https://www.sbtv.com/live/11937/wfmz'
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--verbose', u'https://www.sbtv.com/live/11937/wfmz']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2020.06.16.1
[debug] Python version 2.7.16 (CPython) - Darwin-19.5.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 4.3, ffprobe 4.3, rtmpdump 2.4
[debug] Proxy map: {}
[generic] wfmz: Requesting header
WARNING: Falling back on generic information extractor.
[generic] wfmz: Downloading webpage
[generic] wfmz: Extracting information
ERROR: Unsupported URL: https://www.sbtv.com/live/11937/wfmz
Traceback (most recent call last):
File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 2387, in _real_extract
doc = compat_etree_fromstring(webpage.encode('utf-8'))
File "/usr/local/bin/youtube-dl/youtube_dl/compat.py", line 2562, in compat_etree_fromstring
doc = _XML(text, parser=etree.XMLParser(target=_TreeBuilder(element_factory=_element_factory)))
File "/usr/local/bin/youtube-dl/youtube_dl/compat.py", line 2551, in _XML
parser.feed(text)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1659, in feed
self._raiseerror(v)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1523, in _raiseerror
raise err
ParseError: not well-formed (invalid token): line 6, column 30
Traceback (most recent call last):
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 797, in extract_info
ie_result = ie.extract(url)
File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 530, in extract
ie_result = self._real_extract(url)
File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 3382, in _real_extract
raise UnsupportedError(url)
UnsupportedError: Unsupported URL: https://www.sbtv.com/live/11937/wfmz