Add configuration to run CI with GitHub actions (aces#7128)

Given the changes to Travis pricing which are changing
at the end of the year and the long VM startup times
we've been experiencing lately, this adds a configuration
for GitHub actions to run our continuous integration
directly on GitHub.

The .travis.yml is kept around for now, but will likely
eventually be removed. PHP 7.4 is also removed from the
Travis configuration, because  there's a bug where both "PHP 7.3" and "PHP 7.4"
are running PHP 7.3 under docker with our current configuration.
(The bug is fixed in the GitHub actions configurations, but
given that we'll be moving away from Travis, isn't worth fixing
there.)

.github/workflows/loristest.yml

@@ -20,12 +20,15 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+<<<<<<< 901cf25af321075c87c7db8b0389b3ffe4a027e0
     - name: Setup PHP
       uses: shivammathur/setup-php@v2
       with:
         php-version: ${{ matrix.php }}
         extensions: zip, php${{ matrix.php }}-ast
 
+=======
+>>>>>>> Add configuration to run CI with GitHub actions (#7128)
     - name: Validate composer.json and composer.lock
       run: composer validate
 
@@ -42,7 +45,11 @@ jobs:
       run: sed -i "s/7.3/${{ matrix.php }}/g" Dockerfile.test.php7
 
     - name: Install OS package dependencies
+<<<<<<< 901cf25af321075c87c7db8b0389b3ffe4a027e0
       run: sudo apt-get install php${{ matrix.php }}-ast
+=======
+      run: sudo apt-get install php-ast
+>>>>>>> Add configuration to run CI with GitHub actions (#7128)
 
     - name: Install composer dependencies
       if: steps.composer-cache.outputs.cache-hit != 'true'

.travis.yml

@@ -2,7 +2,6 @@ language: php
 
 php: 
   - 7.3
-  - 7.4
 
 # Testing Ubuntu 18.04
 os: linux