Add CI Pipeline

.gitlab-ci.yml

+variables:
+  DOTNET_CLI_TELEMETRY_OPTOUT: 1
+  
+build:windows:
+  stage: build
+  tags:
+    - windows
+  script:
+    - cd Symfony-api-doc-generator
+    - dotnet restore
+    - dotnet publish  -o ../symfony-api-doc -r win-x64 -p:PublishSingleFile=true --self-contained false
+  artifacts:
+    name: symfony-api-doc-win
+    paths:
+      - symfony-api-doc
+
+build:linux:
+  stage: build
+  image: mcr.microsoft.com/dotnet/sdk:6.0
+  script:
+    - cd Symfony-api-doc-generator
+    - dotnet restore
+    - dotnet publish  -o ../symfony-api-doc -r linux-x64 -p:PublishSingleFile=true --self-contained false
+  artifacts:
+    name: symfony-api-doc-linux
+    paths:
+      - symfony-api-doc
+
+build:macos:
+  stage: build
+  tags:
+    - macos
+  script:
+    - cd Symfony-api-doc-generator
+    - dotnet restore
+    - dotnet publish  -o ../symfony-api-doc -r osx-x64 -p:PublishSingleFile=true --self-contained false
+  artifacts:
+    name: symfony-api-doc-macos
+    paths:
+      - symfony-api-doc