Add code block formatting to the README.md.

[Nufflee]

This adds C code highlighting and proper code block formatting to the example code in the README.md. It makes it a lot nicer and easier to read.

[majianjia]

Great work, please merge @BoschSensortec

[sangvikh]

+1 Just thought of doing this myself. But it should be able to do it by indenting the code with an extra tab, makes the code more copy-pasteable without a markdown viewer. The same can also be applied on DataSync.md https://daringfireball.net/projects/markdown/syntax#precode