Update CI workflow to trigger CI only on code level changes (#906)

This commit adjusts so that changes in documentation files like .md and
.txt, as well as those under api/docs and build/charts directories, no
longer trigger PR events.

The current CI workflow primarily uses Docker Compose to set up a
local development environment for building, testing, linting,
benchmarking, and shard testing the Go project.

Changes under api/docs appear to be documented in swagger via the
openapi spec, and under build/charts are related to Helm charts.

However, changes in api/docs and build/charts seem unrelated to the
current CI process and are likely handled during deployment instead.
Therefore, I adjust not to trigger CI on PR events.

.github/workflows/ci.yml

@@ -5,6 +5,12 @@ on:
     branches: [ main ]
   pull_request:
     branches: [ main ]
+    paths-ignore:
+      - 'api/docs/**'
+      - 'build/charts/**'
+      - '**/*.md'
+      - '**/*.txt'
+      - '**/.gitignore'
 
 env:
   GO_VERSION: '1.21'