Syntax Lookup: Add labeled args

Author: fhammerschmidt

misc_docs/syntax/language_labeled_argument.mdx

@@ -0,0 +1,36 @@
+---
+id: "labeled-argument"
+keywords: ["labeled", "argument"]
+name: "~arg"
+summary: "This is a `labeled argument`."
+category: "languageconstructs"
+---
+
+When declaring a function, arguments can be prefixed with `~` which means that they can and need to be called by their name, not the argument position. This is especially useful to differentiate them more easily if they are of the same type.
+
+### Example
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res
+let calculateDistance = (~x1, ~y1, ~x2, ~y2) => {
+  Math.sqrt((x1 -. x2) ** 2. +. (y1 -. y2) ** 2.)
+}
+
+calculateDistance(~x1=6., ~y1=8., ~x2=3., ~y2=4.) 
+```
+
+```js
+function calculateDistance(x1, y1, x2, y2) {
+  return Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
+}
+
+calculateDistance(6, 8, 3, 4);
+```
+
+</CodeTab>
+
+### References
+
+* [Labeled Arguments](/docs/manual/latest/function#labeled-arguments)
+* [Function Syntax Cheatsheet](/docs/manual/latest/function#tips--tricks)