ci(workflow): add path filters to build workflow (#28)

Only trigger builds when relevant files change:
- src/** (library source code)
- .github/workflows/build.yml (workflow itself)

Prevents unnecessary builds from documentation changes.

Author: CalvinAllen

.github/workflows/build.yml

@@ -3,8 +3,14 @@ name: Build
 on:
   push:
     branches: [ main, develop ]
+    paths:
+      - 'src/**'
+      - '.github/workflows/build.yml'
   pull_request:
     branches: [ main ]
+    paths:
+      - 'src/**'
+      - '.github/workflows/build.yml'
 
 jobs:
   build: