Function decimalNumber

decimalNumber(val: number): number
Validates and converts a number to an integer (decimal number).

Reference: ST_DecimalNumber in OOXML specification
Parameters
- val: number
  The number to validate and convert
Returns number
The floored integer value
Throws
Error if the value is NaN
Example
```
const num = decimalNumber(10.7); // Returns 10
const negative = decimalNumber(-5.3); // Returns -5
```
- Defined in util/values.ts:99