Adds an tiny example on how to use the lib

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Documents the QTXDG_QT_LIBRARIES variable

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Reformatting for an easy reading in a 80x24 terminal

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Updates buildsystem typical use documentation

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Merge pull request #3 from luis-pereira/doc

doc