refactor: backport changes from noatu's fork

feat(style)!: remove reference styling & fix figure numbering for appendices
feat!: swap appending on 'none' being the first position in ..sink
feat: add chapters to pz-lb()
feat: add asserts
fix: better control flow

img() function now requires `none` to be the first position in ..sink,
e.g. `#img("/fig/1.png", "Caption", none)` to get "Caption (рисунок виконано самостійно)" caption.

Use `@some_label[див. рис.]` to get a "див. рис. 42" link.

Signed-off-by: unexplrd <unexplrd@linerds.us>

README.md

@@ -75,7 +75,7 @@ Some text
 // If you ever need appendices in pz-lb template use the show rule
 // WARNING: when using coursework template use its own argument,
 // so it can put bibliography before appendices
-#show: appendices_style
+#show: appendices-style
 
 = Quote
 #link("https://youtu.be/bJQj1uKtnus")[