This is a built-in feature in many Windows applications.
That is, simply move the cursor to the edge of a window (you'll know when the cursor is in the correct position because it will turn into a double-headed arrow), then left-click and drag to resize.
If you move the cursor to a corner, the cursor will be a diagonal double-headed arrow, and you can resize in both directions at once. Otherwise, it'll be a horizontal or vertical one, and resizing is in one direction only.
As a caveat, however, be aware that some applications may not allow resizing of their windows (though this is arguably uncommon).
Since it appears you want the exact same functionality, stroke for stroke, this Super User question may be of interest. The top answer is for a program called AltDrag, which appears to do what you want (hold down Alt and right-click/drag anywhere in a window to resize it).