feat: remove unecessary files from built image

.slugignore

@@ -0,0 +1,35 @@
+.circleci
+.github
+app
+assets
+components
+config
+docs
+lang
+layouts
+middleware
+modules
+node_modules
+pages
+plugins
+scripts
+services
+static
+tests
+.babelrc
+.buildpacks
+.editorconfig
+.eslintrc.js
+.gitignore
+.nvmrc
+.prettierrc
+CHANGELOG.md
+docker-compose.yml
+jest.config.js
+jsconfig.json
+nuxt.config.js
+package*.json
+README.md
+sample.env
+scalingo.json
+tests.sh