chore: update gitignore list (#9437)

Updated the gitignore list with the command : `go run scripts/generate-gitignores.go`

options/gitignore/Phoenix

@@ -0,0 +1,22 @@
+# gitignore template for Phoenix projects
+# website: http://www.phoenixframework.org/
+#
+# Recommended template: Elixir.gitignore
+
+# Temporary files
+/tmp
+
+# Static artifacts
+/node_modules
+/assets/node_modules
+
+# Since we are building assets from web/static,
+# we ignore priv/static. You may want to comment
+# this depending on your deployment strategy.
+/priv/static/
+
+# Installer-related files
+/installer/_build
+/installer/tmp
+/installer/doc
+/installer/deps