🛠️ chore(CI): Add push trigger in all actions

Author: NestorDP

.github/workflows/lint.yml

@@ -1,6 +1,9 @@
 name: Lint
 
 on:
+  push:
+    branches:
+      - main
   pull_request:
     branches:
       - main

.github/workflows/unit-tests.yml

@@ -1,6 +1,9 @@
 name: unit-tests
 
 on:
+  push:
+    branches:
+      - main
   pull_request:
     branches:
       - main

README.md

@@ -2,6 +2,7 @@
 
 [![unit-tests](https://github.com/NestorDP/cppserial/actions/workflows/unit-tests.yml/badge.svg)](https://github.com/NestorDP/cppserial/actions/workflows/unit-tests.yml)
 [![coverage](https://github.com/NestorDP/cppserial/actions/workflows/coverage.yml/badge.svg)](https://github.com/NestorDP/cppserial/actions/workflows/coverage.yml)
+[![codecov](https://codecov.io/gh/NestorDP/cppserial/branch/main/graph/badge.svg)](https://codecov.io/gh/NestorDP/cppserial)
 
 **C++ Application Programming Interface for the `asm/termbits.h` C library**