Add PHP 7.4 tests. (#294)

Author: lucasmichot

.circleci/config.yml

@@ -1,8 +1,8 @@
 version: 2
 jobs:
-  test-7.3: &test-template
+  test-7.4: &test-template
     docker:
-      - image: circleci/php:7.3
+      - image: circleci/php:7.4
 
     working_directory: ~/intercom-php
 
@@ -12,6 +12,11 @@ jobs:
       - run: vendor/bin/phpunit
       - run: vendor/bin/phpcs --standard=PSR2 src test
 
+  test-7.3:
+    <<: *test-template
+    docker:
+      - image: circleci/php:7.3
+
   test-7.2:
     <<: *test-template
     docker:
@@ -26,6 +31,7 @@ workflows:
   version: 2
   test_on_supported_php_versions:
     jobs:
+      - test-7.4
       - test-7.3
       - test-7.2
       - test-7.1