update lib.typ

contrib/typst/variables/lib.typ

@@ -1,6 +1,21 @@
+//! This is a stub package for typst.ts's dyn-svg controlling the layout
+//! Here is a good example of dynamic layout template: <https://github.com/Myriad-Dreamin/typst-book/blob/308e0aacc2578e9a0c424d20332c6711d1df8d1c/contrib/typst/gh-pages.typ>
 
-// It is in default A4 paper size
-#let page-width = 595.28pt
-
-// default target is "pdf"
+/// default target is "pdf", typst.ts will set it to "web" when rendering to a
+/// dynamic layout
+/// Example:
+/// ```typc
+/// #let is-web-target() = target.starts-with("web")
+/// #let is-pdf-target() = target.starts-with("pdf")
+/// ```
 #let target = "pdf"
+
+/// It is in default A4 paper size
+/// example:
+/// ```typc
+/// set page(
+///   width: page-width,
+///   height: auto, // Also, for a website, we don't need pagination.
+/// ) if is-web-target;
+/// ```
+#let page-width = 595.28pt