Function isBlank

isBlank(text?: null | string): boolean
Returns whether the given string is blank
Parameters
- Optionaltext: null | string
  the string to check
Returns boolean
whether the given string is blank
Author
David Hsing

Remarks
check if all the characters in the given string are whitespace or line separators
Example
```
isBlank(undefined);    // true
isBlank('foobar');    // false
```