[compat] BBC iPlayer

[hensm]

App name: BBC iPlayer
App URL: https://www.bbc.co.uk/iplayer/
App ID (if possible):

Issues:
Mostly functional. Some issues with player becoming unresponsive. Captions don't work.

Error log (if applicable):

fx_cast (Debug): cast.addReceiverActionListener  index.ts:47:9
XML Parsing Error: syntax error
    Location: https://emp.bbc.co.uk/emp/SMPj/2.23.17/iframe.html
    Line Number 1, Column 1:  iframe.html:1:1
fx_cast (Debug): cast.requestSession  index.ts:75:9
fx_cast (Debug): Selected receiver  index.ts:130:13
XML Parsing Error: syntax error
    Location: https://emp.bbc.co.uk/emp/SMPj/2.23.17/iframe.html
    Line Number 1, Column 1:  iframe.html:1:1
TypeError: t.mediaSession.customData is null   bump-4.js:2:25695
    onMediaStatusUpdate  https://emp.bbci.co.uk/emp/bump-4/bump-4.js:2:25695
    onMediaStatusUpdate self-hosted:974:17 Media/<
    webpack:///./src/shim/media/classes/Media.ts?:73:25
    onMessage/<  webpack:///./src/shim/messageBridge.ts?:9:9
    sendMessage  webpack:///./src/shim/messageBridge.ts?:28:5
    apply self-hosted:4557:5 applySafeWithoutClone  resource://gre/modules/ExtensionCommon.jsm:527:16
    asyncWithoutClone/<  resource://gre/modules/ExtensionCommon.jsm:2234:20