message: Add `split_at` at manual
diff: @@ -456,6 +456,7 @@ echo $unescape($line)
  The following are the currently-supported array methods.
  - [split](#split)
  +- [split_at](#split_at)
  - [bytes](#bytes)
  - [chars](#chars)
  - [graphemes](#graphemes)
  @@ -489,6 +490,28 @@ age
  data
  ```
  +### split_at
  +
  +Defaults to string variables. The supplied string will be split in two pieces, from the index specified in the second argument.
  +
  +#### Examples
  +
  +```
  +echo @split_at("FOOBAR", "3")
  +echo @split_at("FOOBAR")
  +echo @split_at("FOOBAR", "-1")
  +echo @split_at("FOOBAR", "8")
  +```
  +
  +#### Output
  +
  +```
  +FOO BAR
  +ion: split_at: requires an argument
  +ion: split_at: requires a valid number as an argument
  +ion: split_at: value is out of bounds
  +```
  +
  ### bytes
  Defaults to string variables. Returns an array where the given input string is split by bytes and
  