Add Oireachtas TV Support

[pi-rhoman]

Checklist

• I'm reporting a new site support
• I've verified that I'm running youtube-dl version 2020.03.06
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar issues including closed ones

Example URLs

• Live Video: https://www.oireachtas.ie/en/oireachtas-tv/oireachtas-tv-channel/
• Dáil Video: https://www.oireachtas.ie/en/oireachtas-tv/video-archive/dail-videos/3160
• Seanad Video: https://www.oireachtas.ie/en/oireachtas-tv/video-archive/seanad-videos/3158
• Committies Video: https://www.oireachtas.ie/en/oireachtas-tv/video-archive/committees/3146
• Irish sign language: https://www.oireachtas.ie/en/oireachtas-tv/oireachtas-tv-productions/isl-videos/3150
• Oireachtas TV monthly: https://www.oireachtas.ie/en/oireachtas-tv/oireachtas-tv-productions/oireachtas-tv-monthly/3162
• Oireachtas TV documentaries: https://www.oireachtas.ie/en/oireachtas-tv/oireachtas-tv-productions/oireachtas-tv-documentaries/3161

Description

It would be nice if we could download videos from Dáil Éireann as is supported for several other parliaments.
Oireachtas.ie has historical videos up until 2018 but newer videos must be streamed.
Oireachtas.ie also has it's own productions but direct links to the videos are difficult to come by