add at and sort methods for StaticArray (#103)

Author: MaxGraey

src/stdlib/staticarray.md

@@ -43,6 +43,11 @@ The StaticArray API is similar to the [Array API](./array.md), with the importan
 
 ### Methods
 
+* ```ts
+  function at(pos: i32): T
+  ```
+  Gets the element at the specified position. This method allows for positive and negative integers. Negative integers count back from the last element.
+
 * ```ts
   function concat(other: T[]): T[]
   ```
@@ -73,6 +78,11 @@ The StaticArray API is similar to the [Array API](./array.md), with the importan
   ```
   Returns a shallow copy of this static array's values from `begin` inclusive to `end` exclusive, as a new normal array. If omitted, `end` defaults to the end of the array.
 
+* ```ts
+  function sort(fn?: (a: T, b: T) => i32): this
+  ```
+  Sorts the values of the array in place, using the specified comparator function, modifying the array before returning it. The comparator returning a negative value means `a < b`, a positive value means `a > b` and `0` means that both are equal. Unlike in JavaScript, where an implicit conversion to strings is performed, the comparator defaults to compare two values of type `T`.
+
 * ```ts
   function toString(): string
   ```