README: Review
README: Review

Quick pass over to fix few typos like extra or missing letter.
Simplified the wording in a few places.

Signed-off-by: Ian Rickards <d8a5f1bafabde3317986d41668f5ef557730f0fb@arm.com>

credp/lisa,credp/lisa,credp/lisa,mdigiorgio/lisa,joelagnel/lisa,joelagnel/lisa,bjackman/lisa,bjackman/lisa,ARM-software/lisa,JaviMerino/lisa,arnoldlu/lisa,credp/lisa,ARM-software/lisa,arnoldlu/lisa,mdigiorgio/lisa,ARM-software/lisa,ARM-software/lisa