### String Functions

#### decodeutf8

Accepts a byte value representing a UTF-8 encoded string and return the string.

#### encodeutf8

Accepts a string argument and returns the bytes that represent its UTF-8 encoding.

#### concat

Concats two strings.

#### split

Splits a string using a separator

Example:

```
let parts = split(",", "a,b,c") -- returns ["a", "b", "c"]
```

#### join

Join string in the first argument by placing the string in the second argument
in between.

Example:

```
let parts = join(",", ["a", "b", "c"]) -- returns "a,b,c"
```