Add gh orgs of Singapore government entities

LoneRifle · web-flow · commit 361c798d1367 · 2020-05-21T10:51:27.000+08:00
Taken partially from developer.gov.sg
diff --git a/_data/governments.yml b/_data/governments.yml
@@ -420,6 +420,9 @@ Saudi Arabia:
 Singapore:
   - govtechsg
   - moexmen
+  - opengovsg
+  - dsaidgovsg
+  - govtechsiot
 
 South Africa:
   - eddZA
