Update diagrams

Author: Alberto Sonnino

primary/README.md

@@ -1,6 +1,6 @@
-# Worker Diagram
+# Primary Diagram
 The diagram below illustrates the primary's architecture and could be useful to keep in mind while going through the code.
 
 <p align="center">
-  <img src="https://github.com/facebookresearch/narwhal/blob/master/.assets/diagram-primary.jpg">
+  <img src="https://github.com/facebookresearch/narwhal/blob/master/.assets/diagram-primary.svg">
 </p>

worker/README.md

@@ -2,5 +2,5 @@
 The diagram below illustrates the worker's architecture and could be useful to keep in mind while going through the code.
 
 <p align="center">
-  <img src="https://github.com/facebookresearch/narwhal/blob/master/.assets/diagram-worker.jpg">
+  <img src="https://github.com/facebookresearch/narwhal/blob/master/.assets/diagram-worker.svg">
 </p>