Script producing maps, add a README file automatically produced

I should produce one when producing the maps.

#dx.fits represents the value of the deflection in the x(horizontal) axis normalised to a DLS/DS=1 #dy.fits represents the value of the deflection in the y(vertical) axis normalized to a DLS/DS=1 #g.fits represents the shear field at a DLS/DS=1 #k.fits represents the convergence at a DLS/DS=1 #m.fits represents the mass density in 10^12Msol/kpc^2 #mag10.fits represents the magnification map at redshifts z=10 #mag2.fits represents the magnification map at redshifts z=2 #mag3.fits represents the magnification map at redshifts z=3 #mag4.fits represents the magnification map at redshifts z=4 #mag5.fits represents the magnification map at redshifts z=5 #mag6.fits represents the magnification map at redshifts z=6 #mag7.fits represents the magnification map at redshifts z=7 #mag8.fits represents the magnification map at redshifts z=8 #mag9.fits represents the magnification map at redshifts z=9 #p.fits represents the lensing potential normalised to a DLS/DS=1