add links to preprint

README.md

-
 # Additional Supporting Information for the Manuscript:
 
-> ## Occurrence and Distribution of Pharmaceuticals and their Transformation Products in Luxembourgish Surface Waters 									
+> ## [Occurrence and Distribution of Pharmaceuticals and their Transformation Products in Luxembourgish Surface Waters](https://doi.org/10.26434/chemrxiv.14564301.v1) 									
 >
 > ### Randolph R. Singh<sup>1†\*</sup>, Adelene Lai<sup>1,2</sup>, Jessy Krier<sup>1</sup>, Todor Kondic<sup>1</sup>, Philippe Diderich<sup>3</sup>, Emma L. Schymanski<sup>1\*</sup>							
 >
@@ -25,7 +24,7 @@ Singh, Randolph, Lai, Adelene, Krier, Jessy, Kondic, Todor, Diderich, Philippe,
 
 
 
-This repository contains Additional Supporting Information to the above manuscript. It contains all code and inputs used as described in detail in the Methods section of the manuscript. It is organised as:
+This repository contains Additional Supporting Information to the above manuscript ([preprint](https://doi.org/10.26434/chemrxiv.14564301.v1)). It contains all code and inputs used as described in detail in the Methods section of the manuscript. It is organised as:
 
 
 | Subdirectory   |   Description                                                                                |