New Features
* Comments! 💬
* A new `Comment` object is now used to store comments for submissions and journals
* The comments are organised in a tree structure, and each one contains references to both its parent
object (`Submission` or `Journal`) and, if the comment is a reply, to its parent comment too
* The auxiliary functions `faapi.comment.flatten_comments` and `faapi.comment.sort_comments` allow to flatten the
comment tree or reorganise it
* Separate `JournalPartial` and `Journal` objects
* The new `JournalPartial` class takes the place of the previous `Journal` class, and it is now used only to parse
journal from a user's journals folder
* The new `Journal` class contains the same fields as `JournalPartial` with the addition of comments, and it is only
used to parse journal pages
* Comparisons
* All objects can now be used with the comparison (==) operator with other objects of the same type or the type of
their key property (`id: int` for submissions and journals, and `name_url: str` for users)
Changes
* The `cookies` argument of `FAAPI` is now mandatory, and an `Unauthorized` exception is raised if `FAAPI` is
initialised with an empty cookies list
* The list of `Submission`/`Journal` objects returned by `FAAPI.gallery`, `FAAPI.scraps`, and `FAAPI.journals` now uses
a shared `UserPartial` object in the `author` variable (i.e. changing a property of the author in one object of the
list will change it for the others as well)
Fixes
* Fix path checking against robots.txt not working correctly with paths missing a leading forward slash