[Feature Request]: Otis Theme Base option

### Guidelines

- [X] I have searched the issue tracker for [open](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aopen+is%3Aissue) and [closed](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aissue+is%3Aclosed) issues that are similar to the feature request I want to file, without success.
- [X] I have searched the [documentation](https://docs.freetubeapp.io/) 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

Is it possible to add a Otis Forest theme option in settings for the Base theme?

### Proposed Solution

Here is example:

Hex color: #1b2127, RGB: {27, 33, 39)

Hex color: #1e252, RGB: {30. 37, 44}

### Alternatives Considered

Alternative example option:

### Issue Labels

new optional setting, visual improvement

### Additional Information

Accent color suggestion for the Main and Secondary color for the proposed theme

Hex: #6a7c80
RGB: {106, 124, 128}

Hex: #949494
RGB: {148, 148, 148}