[FEATURE] Add validation

[Hardcore-fs]

🤔 Problem Statement

be able to build blank templates from predefined models
add validation to cols , based on type.

allow lists to be generated on secondary sheets, that can feed data validation on primary sheet.
Also be able to add lists for drop downs , from a secondary data-source into secondary sheets.

💡 Proposed Solution

allow code to build empty templates by adding predefined models to a set of cols/rows and then building
validation formula , as ether inline functions (upto 256 char)
or allowing a specific col to map to an external excel sheet.
that can be prefilled with a range of values (from drop down list)

🔄 Alternatives Considered

writing it myself

📋 Use Case

wold extend current library

🛠️ Implementation Ideas

Datasource rows -> predefined DTO model

DTO
Animals string.

main sheet column Animals with a drop down list, from sheet n
Sheet n animals

cat
dog
rabbit
bird

call routine.
inserts col on sheet 1 called animals, sheet 2 builds list of animals from iterative model.

maps cell range on page 2 to data validation on page 1

📝 Additional Context

No response

✅ Checklist

• I have searched for existing feature requests
• I have provided a clear use case
• This feature would benefit the community