attempt to recognize when holes in timeline for various reasons, clear timeline and fetch older when showing new to get rid of holes

Move custom theming from settings to style-switcher, remove usage of custom .css files, use styles.json instead.

Also fetch user if not in the state already.

Add an option to automatically show new posts when scrolled to the top, also add fade-in animation for posts.

notifications support (doesn't work for native KDE notifications for me tho)

Add floating status-previews on reply-link mouseover in conversations and make them optional in the settings, fix a small visual inconsistency in muted statuses while editing the file already..

Add an option to initiate fetching older statuses automatically when scrolled 750 pixels or less from the bottom.