Run CI only when relevant directories are modified

This avoids spawning dozens of jobs when modifying unrelated files (like README,
documentation, etc...)

Author: giordano

.github/workflows/UnitTests.yml

@@ -1,11 +1,20 @@
-name: Unit Tests
+name: MPI.jl Unit Tests
 
 on:
   pull_request:
-
+    paths:
+      - 'bin/**'
+      - 'deps/**'
+      - 'src/**'
+      - 'test/**'
   push:
     branches:
       - master
+    paths:
+      - 'bin/**'
+      - 'deps/**'
+      - 'src/**'
+      - 'test/**'
 
 jobs:
   test-jll:
@@ -17,9 +26,6 @@ jobs:
           - ubuntu-latest
           - windows-latest
         julia_version:
-          # Unsupported - "1.3"
-          # Unsupported - "1.4"
-          # Unsupported - "1.5"
           - "1.6"
           - "1.7"
           - "nightly"