update translation guide

Author: NullPointerException

README.md

@@ -53,6 +53,8 @@ Issues and PRs are welcomed. Any service related to otaku culture, and any new f
 
 ⚠️Warning: This fork is already far from the main repo. You may have to spend a considerable amount of time resolving conflicts.
 
+If you want to contribute your translation, see [TRANSLATION.md](TRANSLATION.md).
+
 ## Note
 
 This repo exists originally because BiliBili service is rejected by the team due to censorship concerns. Please **DO NOT** raise any issue about merging new services to upstream in this repo, [TeamNewPipe/NewPipe](https://github.com/TeamNewPipe/NewPipe), or [TeamNewPipe/NewPipeExtractor](https://github.com/TeamNewPipe/NewPipeExtractor/). It is **MEANINGLESS** and a **WASTE OF TIME** for the maintainers.

TRANSLATION.md

@@ -0,0 +1,21 @@
+Thanks for your interest in contributing to the translation!
+
+## If you know how to use git to clone, modify and then make a pull request
+
+Just clone the client, open `app/src/main/res/values/strings.xml` and find the untranslated strings. The string is like that:
+```agsl
+<string name="title_activity_about">About AnimePipe</string>
+```
+there the name is the key, and the content is the value. Copy this line and paste it to the end of the your language's file, which can be found in the same directory. Then translate the value. 
+
+For example, if you are translating to Simplified Chinese, you should paste the line to the end of `app/src/main/res/values-b+zh+HANS+CN/strings.xml`. Then translate the value to Chinese. The result should be like this:
+```agsl
+<string name="title_activity_about">关于AnimePipe</string>
+```
+When you finish your translation you can make a pull request.
+
+## If you don't know how to use git
+
+You can just ignore the clone step and open string.xml [online](https://codeberg.org/NullPointerException/AnimePipeClient/src/branch/dev/app/src/main/res/values/strings.xml)
+then follow the same steps above. You can also modify your language's file online, and then it will automatically make a pull request.
+For example, the link to the Simplified Chinese file is [here](https://codeberg.org/NullPointerException/AnimePipeClient/src/branch/dev/app/src/main/res/values-b+zh+HANS+CN/strings.xml).