Update README.txt with changelog and minor text improvements

updated readme with 'Tested up to' to 6.5.3

mastadon logo change and php checker fix

minor changes

Merge pull request #25 from superwebshare/2.4

Text color added for AMP social icons and floating

Typo fix in props

Update IT language files

Update public js with new minify

Update AMP CSS minify

set default color as white for the appearance