Function parseCronStartOrBlank

parseCronStartOrBlank(source: string): undefined | "?"
Parses CronStartOrBlank into a string.

Example
```
parseCronStartOrBlank("?"); // "?"
parseCronStartOrBlank("💩"); // undefined
```
Returns
A string or undefined if invalid.
Parameters
- source: string
  
  CronStartOrBlank to be parsed.
Returns undefined | "?"
- Defined in src/parsers/parseCronStartOrBlank.ts:15