Multi-sort for data tables

## Summary
Multi-sort provides the user with the ability to sort by multiple columns at once. With the data sorted intially by the primary sort, then secondarily by the secondary sort.

## 💰 User value
Provides additional ability to sort data to ease location and comparison.

## 📚 User Stories
If relevant, describe the high-level functionality as user stories.

*As an* ICDS user:
*I need* to be able to apply multi-sort to columns in a data table
*So that* I can better control the data within a table.

*An an* ICDS User
*I need* to be able to add multiple concurrent sorts, and see which sort is ordered where,
*So that* I have better control over my data.

## 📝 Acceptance Criteria
If relevant, describe in full detail the different interactions and edge cases that the component or patterns needs to fulfil.

**Multi-sort**
*Given* that one column is already sorted
*When* clicking on another column and holding down the sort key (windows=ctrl, mac=cmd, or shift on either)
*Then* the new sort is added and each columns sort is identified by a numbered badge.

## ✏ Designs
If there's a Figma design file (or other mock-up), include it here.

## 🧾 Guidance
If there's written guidance or documentation, include it here.

No files or tests are named. Start by locating the data-table component and its existing sorting behavior and tests, then trace how keyboard-modified column clicks are handled. Done means multiple concurrent sorts work, their order is shown with numbered badges, and the relevant tests cover the accepted interaction.

Written by the indexing model from the issue text.