Symbol docstrings (#7983)

Author: fhammerschmidt

packages/@rescript/runtime/Stdlib_Symbol.resi

@@ -85,20 +85,97 @@ Symbol.toString(sym) == "Symbol(sym1)"
 @send
 external toString: t => string = "toString"
 
+/**
+`asyncIterator` is the well-known symbol used by asynchronous iterables.
+
+See [`Symbol.asyncIterator`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/asyncIterator) on MDN.
+*/
 @val @scope("Symbol")
 external asyncIterator: t = "asyncIterator"
+
+/**
+`hasInstance` is used by custom `instanceof` checks.
+
+See [`Symbol.hasInstance`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/hasInstance) on MDN.
+*/
 @val @scope("Symbol")
 external hasInstance: t = "hasInstance"
+
+/**
+`isConcatSpreadable` controls whether objects are flattened when passed to `Array.concat`.
+
+See [`Symbol.isConcatSpreadable`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/isConcatSpreadable) on MDN.
+*/
 @val @scope("Symbol") external isConcatSpreadable: t = "isConcatSpreadable"
+
+/**
+`iterator` is returned by objects that can be iterated with `for..of`.
+
+See [`Symbol.iterator`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator) on MDN.
+*/
 @val @scope("Symbol") external iterator: t = "iterator"
+
+/**
+`match` customises how values respond to `String.prototype.match`.
+
+See [`Symbol.match`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/match) on MDN.
+*/
 @val @scope("Symbol") external match: t = "match"
+
+/**
+`matchAll` customises how values respond to `String.prototype.matchAll`.
+
+See [`Symbol.matchAll`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/matchAll) on MDN.
+*/
 @val @scope("Symbol") external matchAll: t = "matchAll"
+
+/**
+`replace` customises how values respond to `String.prototype.replace`.
+
+See [`Symbol.replace`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/replace) on MDN.
+*/
 @val @scope("Symbol") external replace: t = "replace"
+
+/**
+`search` customises how values respond to `String.prototype.search`.
+
+See [`Symbol.search`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/search) on MDN.
+*/
 @val @scope("Symbol") external search: t = "search"
+
+/**
+`species` lets constructors return a different derived constructor when methods create new instances.
+
+See [`Symbol.species`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/species) on MDN.
+*/
 @val @scope("Symbol") external species: t = "species"
+
+/**
+`split` customises how values respond to `String.prototype.split`.
+
+See [`Symbol.split`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/split) on MDN.
+*/
 @val @scope("Symbol") external split: t = "split"
+
+/**
+`toPrimitive` customises how objects convert to primitive values.
+
+See [`Symbol.toPrimitive`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toPrimitive) on MDN.
+*/
 @val @scope("Symbol") external toPrimitive: t = "toPrimitive"
+
+/**
+`toStringTag` customises the default tag shown by `Object.prototype.toString`.
+
+See [`Symbol.toStringTag`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag) on MDN.
+*/
 @val @scope("Symbol") external toStringTag: t = "toStringTag"
+
+/**
+`unscopables` marks properties that should be skipped by `with`.
+
+See [`Symbol.unscopables`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/unscopables) on MDN.
+*/
 @val @scope("Symbol") external unscopables: t = "unscopables"
 
 /**