readme: add 'JetBrains' to 'IntelliJ IDEA' as the official name
Revert "readme: make the description for x-parent() more clear"

This was an incorrect description.

This reverts commit a385ca40267ca7a11e83d3f34de0c36e6fd8802e.
Module: introduce x-parent() function

x-parent() function returns the parent Modifier selector,
or returns Module root's selector if the parent Modifier doesn't exist.
Module: make x-extend() compatible with `@extend`