Update getting-started.md: 1.12.13 and releases on github

Author: dpolivaev

src/docs/getting-started/getting-started.md

@@ -4,10 +4,9 @@
 
 [![Download Freeplane](../images/Download.png ':size=71x67')](https://sourceforge.net/projects/freeplane/ ':target=_blank')
 
-<big>**[Download Freeplane now!](https://sourceforge.net/projects/freeplane/ ':target=_blank')** </big>\
-(this downloads the stable version 1.12.12)\
+<big>**[Download Freeplane now!](https://github.com/freeplane/freeplane/releases ':target=_blank')** </big>\
+(this downloads the stable version 1.12.13)\
 [change log](https://www.freeplane.org/info/history/history_en.txt) \
-Download last development versions ( [***preview***](https://sourceforge.net/projects/freeplane/files/freeplane%20preview/) )
 
 → [Find out](Distributions.md) which distribution better fits your requirements.