Fix input filenames with dot `.` parsed incorrectly

[pkong-ds]

ref #69

Problem

Previously, filename parsing method is implemented with custom code like split('.') instead of os.path.splitext()

Solution

Use os.path.splitext instead

Test run

Input

Simulator Screenshot - iPhone 15 Pro Max - 2024-06-15 at 20.53.15	Simulator Screenshot - iPhone 15 Pro Max - 2024-06-15 at 20.53.29

Output

apple-iphone-15-black-mockup(2).zip