requirements: Updated markdown package to v2.3.1
requirements: Updated markdown package to v2.3.1

kerel-fs/skylines,skylines-project/skylines,TobiasLohner/SkyLines,Turbo87/skylines,Harry-R/skylines,Turbo87/skylines,RBE-Avionik/skylines,Harry-R/skylines,snip/skylines,RBE-Avionik/skylines,RBE-Avionik/skylines,shadowoneau/skylines,skylines-project/skylines,snip/skylines,Turbo87/skylines,Harry-R/skylines,shadowoneau/skylines,TobiasLohner/SkyLines,TobiasLohner/SkyLines,RBE-Avionik/skylines,Turbo87/skylines,skylines-project/skylines,snip/skylines,Harry-R/skylines,skylines-project/skylines,kerel-fs/skylines,shadowoneau/skylines,shadowoneau/skylines,kerel-fs/skylines