Feature/introduce script to create changelog (#401)

* Introduce script to create a changelog

* Add information about version to server version mapping

* Add release process doc

CONTRIBUTING.md

@@ -5,6 +5,30 @@ Everything from https://github.com/Suwayomi/Tachidesk-Server/blob/master/CONTRIB
 ## About this project
 This is a `create-react-app` project, you can find it's readme in [BUILDING.md](./BUILDING.md)
 
+## Release process
+1. Update the changelog
+   1. Copy the content of the template changelog to the top of the actual changelog
+   2. Create the changelog since the latest release (printed in console) with `npm run createChangelog -- --sha <latest commit hash of previous release>`
+   3. Copy the changelog to the corresponding position in the template
+   4. Create a TL;DR
+2. Update the [version to server version mapping file](versionToServerVersionMapping.json)
+   1. See [When to update](#when-to-update)
+
+## WebUI to [server](https://github.com/Suwayomi/Tachidesk-Server) mapping
+### Explanation
+For the server to be able to automatically download the latest compatible WebUI version, the [version to server version mapping file](versionToServerVersionMapping.json) has to be provided.<br/>
+
+The order of the version mapping is important and has to be sorted by oldest WebUI version to latest version.<br/>
+The latest version will always be `PREVIEW`.
+
+### When to update
+- changes get added that require a new minimum server version
+    - **update:** the mapped server version for the `PREVIEW` version
+- releasing a new version
+    - **update:** in case the minimum server version has
+        - not changed: the latest WebUI version mapping that is not the `PREVIEW` version has to be updated
+        - changed: add a new entry below the `PREVIEW` version with the mapped server version from `PREVIEW`
+
 ## Coding Style Guide
 **Note:** Some of the bellow are new, refactor the code to match the style guide where you see inconsistency.
 - Don't use relative imports.