This release fixes the "N channels failed to update" message that could appear
for channels that were perfectly fine, and several other bugs.

• Channels that fail to update are now tried again before a category reports
  them. YouTube's feed service answers some requests with an error and the very
  same request correctly moments later, which is what produced most of these
  messages.
• Pressing Refresh now gives you the page back as soon as every channel has been
  asked once, and carries on repairing failed channels in the background. The
  failure count falls while you browse instead of making you wait for it.
• Opening or refreshing a category is quicker, because a channel is no longer
  asked about a feed it has already been shown not to have.
• Marking videos as watched now saves all of them. Previously, marking several
  in a row kept only one — the rest looked ticked until you reloaded the page.
• A new category is now added at the end of the tab row, instead of sometimes
  appearing in the middle if you had deleted categories earlier.
• Importing a list of channels no longer saves channels under the wrong name and
  ID when YouTube returns an incomplete page. Such channels are retried, and any
  that still fail are listed as not imported. If an earlier import left you with
  channels named "Unknown Channel", remove them and import the list again.
• If YouTube's cookie prompt has not been accepted in your browser, adding or
  importing channels now explains that and tells you what to do, instead of
  failing with a generic error.
• A channel with no regular uploads now falls back to showing its live streams,
  instead of appearing empty.
• When YouTube or your connection does not answer, loading a category gives up
  on each channel after 15 seconds instead of up to 30.
• A response that is not a complete feed is now always treated as a failed
  update, so it can never replace a channel's saved videos with an empty list.
• If a category does report failures, the browser console now explains which
  channels failed and what YouTube answered — press F12 on the YT Channels tab,
  open the Console and press Refresh. This is helpful to include in a bug
  report. Nothing is logged when everything loads normally, and nothing is ever
  sent anywhere.

Version 1.2.1
- When YouTube or your connection doesn't answer, loading a category now gives up on each channel after 15 seconds instead of up to 30, so problems show up sooner.
- Importing a list of channels no longer saves a channel under the wrong name and ID when YouTube returns an incomplete page. Those channels are retried, and any that still fail are listed as not imported so you can try them again.
- A response that isn't a complete feed is now always treated as a failed update, so it can never replace a channel's saved videos with an empty list.
- Internal changes: feeds are read without the browser's XML parser, and the toolbar menu item now uses the standard "contextMenus" permission name. There is no new permission prompt and no change to what you see.
- If YouTube's cookie prompt hasn't been accepted in your browser, adding or importing channels now says so and tells you what to do, instead of failing with a generic error.

• Fixed Shorts sometimes lingering in your category feeds, especially after losing and regaining your internet connection. Shorts are now filtered out of every feed, and a failed or slow update can no longer overwrite newer results.
• Refresh now always asks YouTube for fresh data instead of reusing the browser's cache.
New crisp vector icons throughout the Feed and Manage pages, replacing the old text symbols. The extension icon is smoother, comes in more sizes, and now shows in the Feed and Manage page tabs.
• The Manage page now marks channels that only post Shorts ("No long-form videos to show").
• Removing a channel now also clears its saved videos, and old watch-progress entries are tidied up automatically.
• The extension no longer asks for the "Access browser tabs" permission.
• The cache setting is now called "Keep videos fresh for (minutes)".

• Added video watch progress bar.
• Added per category import/exporting.
• Added a page to view category members.

Small bug fixes (amongst of which middle clicking video links didn't work)