ci: Define concurrency groups for cancelling duplicate jobs

This commit will force running jobs of a given PR to be cancelled once
the same branch is updated, avoiding the CI wasting time testing
outdated content.

Signed-off-by: Gustavo Henrique Nihei <gustavo.nihei@espressif.com>
diff --git a/.github/workflows/espressif.yaml b/.github/workflows/espressif.yaml
index 0aac747..ada3067 100644
--- a/.github/workflows/espressif.yaml
+++ b/.github/workflows/espressif.yaml
@@ -10,6 +10,10 @@
 
 name: Espressif
 
+concurrency:
+  group: espressif-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   environment:
     strategy: