Add interfaces

.gitattributes

@@ -14,3 +14,5 @@ composer.lock export-ignore
 phpunit.xml export-ignore
 phpunit.xml.dist export-ignore
 docker export-ignore
+
+* text eol=lf

.github/workflows/continuous-integration.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php-versions: ['7.2', '7.3', '7.4']
+        php-versions: ['7.1', '7.2', '7.3', '7.4', '8.0']
 
     steps:
     - uses: actions/checkout@v2
@@ -22,13 +22,13 @@ jobs:
       run: composer validate
 
     - name: Install dependencies
-      run: composer install --prefer-dist --no-progress --no-suggest
+      run: composer update --prefer-dist --no-progress --no-suggest
 
     - name: PhpUnit
       run: ./vendor/bin/phpunit
 
     - name: Psalm
-      run: ./vendor/bin/psalm --show-info=false --threads=8 --diff --diff-methods
+      run: ./vendor/bin/psalm --show-info=false --threads=8 --diff
 
     - name: PHPCS
       run: ./vendor/bin/phpcs -s --report-source --runtime-set ignore_warnings_on_exit 1