add chapter on openeing reports

docs/7.-Report-Viewer.md

@@ -1,7 +1,25 @@
-## Views
+
 
 ## Opening Reports
 
+The report viewer can be started over the Jar, by specifying a view mode. This is done over the `--mode`/`-M` flag:
+|Value|Effect|
+|---|---|
+| run_and_view (default) | Runs JPlag on the given files with the given options. After Running it opens the report viewer. The report viewer will then automatically load the result. |
+| view | Opens the report viewer. When providing a result zip file from a previous JPlag run - either in a way a source directory would be given or through the `-r` flag. If no file is given the landing page will be opened. |
+| run | Runs JPlag without opening the report viewer. |
+
+### Landing Page
+On the landing page a report can be opened by either dragging the zip file onto the page. Alternatively when clicking the red square a file chooser will open.
+
+Reports can fetched from a server by appending `?file=URL`. Example: `jplag.github.io/JPlag?file=domain.tld/my-report.zip` 
+
+### Reports from older versions
+With increasing versions the report may change and the report viewer may not be able to read a report from an earlier version. 
+When trying to open such a report, the report viewer will redirect you to an older version of the report viewer.
+This older report viewer may not support all the newest features of JPlag.
+This feature is only when starting the report viewer through the jar.
+
 ## Running Locally
 
 ### Setup
@@ -41,6 +59,9 @@ npm run build-demo
 ```
 Similar to the production build, this build will have `demo` as its base url.
 
+## Views
+
+
 ## Contributing
 
 We're happy to incorporate all improvements to JPlag into this codebase. Feel free to fork the project and send pull requests. Please consider [our guidelines for contributions](/~https://github.com/jplag/JPlag/wiki/3.-Contributing-to-JPlag).