Fix indentation (spaces and tabs mix and match)

[DRSDavidSoft]

Hi there, thanks for the library!

I applied some formatting fixes to the code to improve the code readability. Previously, spaces and tabs were both used in the code which made reading it a bit hard.

This PR replaces the spaces to tabs, so when the project is opened into the editor using the tab size of 2 (the default that is used in the Arduino IDE), the correct amount of spacing is used instead.

Can't believe it's been 10 years since this library was created. Thank you for your work! 👍🏻