EXT-X-DATERANGE support

[theRealRobG]

Description

This PR attempts to add EXT-X-DATERANGE as a tag that is recognised by Mamba under PantosTag, along with the attributes that the tag supports. The attributes were taken from draft-pantos-hls-rfc8216bis-05.

Change Notes

• Added new case to PantosTag
• Added new cases to PantosValue
• Added validation for PantosTag.EXT_X_DATERANGE (EXT_X_DATERANGETagValidator)
• Added playlist validation (EXT_X_DATERANGEPlaylistValidator)

Pre-submission Checklist

• [x] I ran the unit tests locally before checking in.
• [x] I made sure there were no compiler warnings before checking in.
• [x] I have written useful documentation for all public code.
• [x] I have written unit tests for this new feature.