add build workflow

.github/workflows/build.yml

@@ -0,0 +1,22 @@
+name: Build firmware
+
+on:
+  push:
+    branches:
+      - "master"
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Installing platformio
+        run: pip3 install -U platformio
+
+      - name: Building a firmware
+        run: |
+          pio lib install
+          pio run

README.md

@@ -3,8 +3,8 @@
   A project to control a peanut, coffee & cocoa roaster with an ESP32
 </p>
 <p align="center">
-  <a href="https://github.com/sindresorhus/awesome">
-    <img alt="Awesome" src="https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg">
+  <a href="https://github.com/gabrielmarcano/esp32-roaster/blob/master/.github/workflows/build.yml">
+    <img alt="Build" src="https://img.shields.io/github/actions/workflow/status/gabrielmarcano/esp32-roaster/build.yml">
   </a>
   <a href="https://github.com/gabrielmarcano/esp32-roaster/releases">
 	<img alt="GitHub release" src="https://img.shields.io/github/v/release/gabrielmarcano/esp32-roaster?filter=*alpha&logo=github">