.github: adjust testing workflow triggers

Run tests and linter on push, PR to master and manually.

Signed-off-by: Anna Shaleva <[email protected]>

.github/workflows/go.yml

@@ -1,5 +1,15 @@
 name: Go
-on: [push]
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches:
+      - master
+    types: [opened, synchronize]
+    paths-ignore:
+      - '**/*.md'
+  workflow_dispatch:
+
 jobs:
   lint:
     name: Lint