started writing lexer after making string lib

string/docs/char_at.md

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+# string_CharAt
+Get character at index in string.
+
+## Arguments
+- str (string): string to get character of.
+- index (int): the index in the string you want to get.
+
+## Returns
+char (string): the character at the specified index in the string.
+
+## Raises
+- `OutOfBounds`: raised if you try accessing a string past its length or at a negative index.
+
+## Example
+### Ground
+```python
+call !string_CharAt "my string" 3 &char
+println $char # "s"
+```
+
+### Solstice
+```c
+puts string_CharAt("my string", 3) // "s"
+```