Add path filter for running the solana CI tests (#134)

Author: barnjamin

.github/workflows/solana.yml

@@ -3,7 +3,9 @@ on:
   push:
     branches:
       - main
-  pull_request: null
+  pull_request: 
+    paths:
+      - 'solana/**'
 
 env:
   RUSTC_VERSION: 1.75.0

.github/workflows/universal-rs.yml

@@ -4,6 +4,8 @@ on:
     push:
         branches: [main]
     pull_request:
+        paths:
+            - 'universal/**'
 
 env:
     CARGO_TERM_COLOR: always