feat: add annotations railroad diagrams

syntax/annotations.typ

@@ -0,0 +1,74 @@
+#import "@preview/fervojo:0.1.1": render
+
+#let value = ```
+{[`value` <
+  [`number` 'digit' * ! <!, ["." 'digit' * !]>],
+  [`boolean` <"False", "True">],
+  [`none` "None"]
+>]}
+```
+
+#let constraint = ```
+{[`constraint` "(" <"_", 'value'> <">", "<", ">=", "<=", "==", "!="> <"_", 'value'> ")"]}
+```
+
+#let type-with-constraints = ```
+{[`type-with-constraints` 'identifier' <!, ["+" 'constraint'] * !>]}
+```
+
+#let column-def = ```
+{[`column-def` <!, ['identifier' ":"]> <"_", 'type-with-constraints'>]}
+```
+
+#let frame-def = ```
+{[`frame-def` 'column-def' * ","]}
+```
+
+#let annotation = ```
+{[`annotation` 'identifier' <!, ["[" 'frame-def' "]"]>]}
+```
+
+#let rules = (
+  value,
+  constraint,
+  type-with-constraints,
+  column-def,
+  frame-def,
+  annotation,
+)
+
+#set text(font: "Source Sans 3")
+
+= Type annotation syntax
+
+#for rule in rules {
+  render(rule)
+}
+
+/*
+#let by-name = (
+  annotation: annotation,
+  frame-def: frame-def,
+  column-def: column-def,
+  type-with-constraints: type-with-constraints,
+  constraint: constraint,
+  value: value,
+)
+
+#let substitute(base-rule) = {
+  let new-rule = base-rule
+  for (key, rule) in by-name.pairs() {
+    new-rule = new-rule.replace("'" + key + "'", rule.text.slice(1, -1))
+  }
+  if new-rule != base-rule {
+    new-rule = substitute(new-rule)
+  }
+  return new-rule
+}
+
+#let combined = raw(substitute(annotation.text))
+
+
+#set page(flipped: true)
+#render(combined)
+*/