docs: translated demo/forking into ja

Author: Msksgm

content/ja/docs/demo/forking.md

@@ -0,0 +1,32 @@
+---
+title: デモリポジトリのフォーク
+linkTitle: フォーク
+---
+
+[デモリポジトリ][] はフォークされて OpenTelemetry で何を行っているかを見せるために設計されています。
+
+Setting up a fork or a demo usually only requires overriding some environment
+variables and possibly replacing some container images.
+
+Live demos can be added to the demo
+[README](https://github.com/open-telemetry/opentelemetry-demo/blob/main/README.md?plain=1).
+
+## Suggestions for Fork Maintainers
+
+- If you'd like to enhance the telemetry data emitted or collected by the demo,
+  then we strongly encourage you to backport your changes to this repository.
+  For vendor or implementation specific changes, a strategy of modifying
+  telemetry in the pipeline via config is preferable to underlying code changes.
+- Extend rather than replace. Adding net-new services that interface with the
+  existing API is a great way to add vendor-specific or tool-specific features
+  that can't be accomplished through telemetry modification.
+- To support extensibility, please use repository or facade patterns around
+  resources like queues, databases, caches, etc. This will allow for different
+  implementations of these services to be shimmed in for different platforms.
+- Please do not attempt to backport vendor or tool-specific enhancements to this
+  repository.
+
+If you have any questions or would like to suggest ways that we can make your
+life easier as a fork maintainer, please open an issue.
+
+[デモリポジトリ]: {{% param repo %}}