refactor: added TextBasedChannels type

[kyranet]

Please describe the changes this PR makes and why it should be merged:

At the moment, if Discord adds a new channel type, we have to update the types in many places, this creates issues as far as the type consistency go, such as MessageCollector not accepting NewsChannel as a valid channel type.

I also considered #6262 as an alternative fix for this, however, a generic type doesn't have many of the benefits from an union, such as being able to exclude certain types (channel.guild ? <channel is TextChannel | NewsChannel | ThreadChannel> : <channel is DMChannel | PartialDMChannel>).

I also made a typedef in the JavaScript side so the documentation for it is readily available in the documentation website, and refactored the TS type for TextBasedChannelTypes to read the new type's type field, so any change we do to TextBasedChannels will reflect on it.

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating
• This PR only includes non-code changes, like changes to documentation, README, etc.
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)