Change conditions when to build Docker container (#328)

Run Docker build if the Dockerfile or any file related to it is changed. Do not automatically run if
notebooks' content is updated, since that update can be easily pulled via git.

Author: edoardob90

.github/workflows/docker-build.yml

@@ -5,20 +5,24 @@ on:
   push:
     branches:
       - main
-    paths-ignore:
-      - "*.md"
-      - slides/**
-      - images/**
-      - .gitignore
+    paths:
+      - "Dockerfile"
+      - "docker/**"
+      - "binder/**"
+      - "**/environment.yml"
+      - "tutorial/tests/testsuite/**"
+      - ".github/workflows/docker-build.yml"
     tags:
       - "v*.*"
       - "v*.*.*"
   pull_request:
-    paths-ignore:
-      - "*.md"
-      - slides/**
-      - images/**
-      - .gitignore
+    paths:
+      - "Dockerfile"
+      - "docker/**"
+      - "binder/**"
+      - "**/environment.yml"
+      - "tutorial/tests/testsuite/**"
+      - ".github/workflows/docker-build.yml"
   workflow_dispatch:
 
 jobs: