T21b and T21c: Documents, reading and knowledge

- DocumentViewer: pages the app drew on a desk, the page under the view's middle
  counted, zoom steps and fit, thumbnails, notes pinned where a press lands, and
  the owner's FindWidget over the pages, hits lit and the current one revealed
- PageThumbnailList, EpubReader (chapters, type size, progress), PrintPreview
- MarkdownRenderer feeds TableOfContents through sections and outline
- Footnote, TooltipTerm, Glossary, ReadingProgress, ZenMode
- Backlinks, Favorites, TrashBin, PageCover, PageIcon, TemplatePicker,
  VersionHistory with PageHistoryDiff
- editor::FindWidget shows the replace fold and option toggles only with handlers
- block editor tests move to documents/blocks
- icons: a-arrow-down, a-arrow-up
- gallery: reading and knowledge sections; scripted find, changes and zen

src/documents/mod.rs

@@ -1,30 +1,49 @@
 mod blocks;
 mod counts;
+mod epub;
+mod find;
 mod format;
+mod history;
+mod knowledge;
 mod link;
 mod markdown;
 mod modes;
+mod pages;
+mod print;
+mod reading;
 mod render;
 mod rich;
 mod suggest;
+mod templates;
 #[cfg(all(test, feature = "test-support"))]
 mod tests;
+mod thumbs;
 mod todo;
 mod toolbar;
 mod tree;
+mod viewer;
 
 use gpui::App;
 
 pub use blocks::{Align, BlockData, BlockEditor, BlockEvent, BlockKind, Media};
 pub use counts::{ReadingTime, WordCount};
+pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};
+pub use history::{PageHistoryDiff, Version, VersionHistory};
+pub use knowledge::{Backlink, Backlinks, Favorite, Favorites, TrashBin, Trashed};
 pub use link::LinkEditor;
 pub use markdown::markdown_highlights;
 pub use modes::{MarkdownEditor, MarkdownMode};
-pub use render::MarkdownRenderer;
+pub use pages::{PageCover, PageIcon};
+pub use print::{Margins, Paper, PrintPreview, PrintSettings, sheet};
+pub use reading::{Footnote, Glossary, ReadingProgress, TooltipTerm, ZenMode};
+pub use render::{MarkdownRenderer, outline};
 pub use rich::RichTextEditor;
+pub use templates::{Template, TemplatePicker};
+pub use thumbs::PageThumbnailList;
 pub use todo::{Checklist, TodoItem};
 pub use toolbar::FixedFormatToolbar;
+pub use viewer::{DocPage, DocumentViewer, PageHit, PageNote};
 
 /// Binds the documents keys. `init` calls it.
 pub(crate) fn bind_keys(cx: &mut App) {