implement automatic journal pagination

[upsuper]

This PR implements automatic pagination for the journal report as a solution to improve performance opening journal page.

At high level, it involves

• journal.html handles page parameter in request.
  • When it's not set, and the total number of entries is larger than a per-page number, it assign the total number of pages to paginated attribute on the <fava-journal> custom element.
  • When it's set, it slices the entries and only render the given page of the entries.
• FavaJournal checks if there is paginated attribute set, it automatically starts fetching all the remaining pages and append them to the <ol>.

With pagination, it's desirable for entries that show up first to be loaded first. Journal table currently renders in date ascendant but the default and most commonly useful order is date descendant, so this PR also changes the rendering order from asc to desc and negate the sort value.

1000 is used as the fixed per-page number because based on my local testing, it is a reasonable balance between initial delay vs. number of pages. It could potentially go up to 2,000.

[upsuper]

@yagebu Would you mind taking a look at the high level approach? If you think this is not going towards the right direction, I can definitely try a different approach.

Several alternatives I can think of:

• Utilize some JSON API endpoint (as oppose to paginating on journal.html).
• Use explicit pagination (i.e. showing page indicators underneath).
• Use lazy pagination (i.e. only load remaining when scrolling to it).

Also it may be useful to take into account the sorting preference. But I think that would significantly increased the complexity without adding much value, because majority of people would likely just default to sorting by date in descending order.

[deirn]

I implemented lazy rendering using virtual lists on the client. #2080