Update README.md documentation syntax/format (#147)
Update README.md documentation syntax/format (#147)

* Fix Linux supported arch indentation in README.md

The indent need to be 2 sapces here, origin one caused wrong rendering
on GitHub project package.

* Remove trailing spaces in README.md

* Fix the blank lines usage in README.md

Heading, fence and list should be surrounded by exactly one blank line.

kamatama41/tfenv,iamhsa/tfenv