Add support to remove specific attachment

[xMohnad]

Is your feature request related to a problem? Please describe.

Currently, pymkv2 lacks direct methods to manage attachments within MKV files. Users cannot easily remove, or list attachments using the MKVFile class, limiting the library's flexibility in handling embedded resources such as fonts, images, etc..

Implementation steps

• Append all attachments to ~MKVFile.attachments similar to how tracks are handled.
• Add a new method remove_attachment(attachment_id) to the MKVFile class.
• Add a new method remove_all_attachments() to remove all attachments not added by the add_attachment(attachment) method. [Optional]
• Update the documentation to include examples and usage instructions for the new methods.

Additional context
To implement this feature, pymkv2 can leverage mkvmerge --attachments !id1,id2,... to exclude specific attachments during remuxing.