Amending Existing Code To Add New Column To Macro Output

Attached is my sample data Sample Data_Combine Sheets.xlsm.

What the code in the attached sheet does is that it combines the data in Sheets Set1 and Set2 into the worksheet named "Combine".

Both input sheets share same columns. Code I use is as below:

VB:
Sub BuildPivotData()
Dim wrsht As Variant
Dim i As Integer

Sheets("Combine").Range("A2:AI500").Clear
wrsht = [{"Set1", "Set2"}]
For i = 1 To UBound(wrsht)
Sheets(wrsht(i)).[a2].CurrentRegion.Offset(1).Copy Sheets("Combine").Range("A65536").End(xlUp)(2)
Next i
End Sub

I want to amend the output in such a way that when the macro is run , in the "Combine" worksheet an additional column is added at the start(col A) with header as "Category".

The category should be nothing but the input Sheet name i.e Set1 or Set2.

Here is an example ... Output Sheet.xlsx.