Release v0.4.0

What's Changed

• docs: small changes and doc fixes by @deven98 in #665
• fix: delayed subscriber offer handling by @Brazol in #666
• fix: fixing iOS speakerphone initialization by @Brazol in #664
• fix: using correct code to disconnect from WS by @Brazol in #667
• fix(dogfooding): dogfooding fixes by @Brazol in #668
• fix: fixed MediaStreamTrack compilation error for web by @Brazol in #657
• chore: dart format by @Brazol in #669
• Release v0.4.0 by @Brazol in #670

Full Changelog: v0.3.9...v0.4.0