[Feature Request]: Include additional information on subscription page if no subscribed channels

Guidelines

[X] I have searched the issue tracker for open and closed issues that are similar to the feature request I want to file, without success.
[X] I have searched the documentation for information that matches the description of the feature request I want to file, without success.
[X] This issue contains only one feature request.

Problem Description

A new user can be confused on where they'd have to go if they have no subscriptions.

Proposed Solution

Solution 1) we provide a link to freetube documentation when subscriptions are empty

problem: how often do people actually look at the documentation if they're not a developer? A lot of people expect things to just work

Solution 2) we provide a message with a link that will bring them to the settings page and scroll to the data settings where they can import subscriptions

Example messages: "your subscriptions are empty. if you wish to import your subscriptions take a look at the freetube documentation (link to freetube docs)"

"Your subscriptions are empty. If you want to import your subscriptions you can go to Data Settings and select Import Subscriptions (link to data settings) or you can search for a channel and subscribe to them"

Alternatives Considered

A link isn't required but we know a lot of users aren't going to read the documentation/don't know the documentation exists unless we send them a link to it.

This could also be part of https://github.com/FreeTubeApp/FreeTube/issues/4332 instead of the subscription message.

Issue Labels

ease of use improvement

Additional Information

No response

FreeTubeApp / FreeTube