docs: write README

Signed-off-by: Conrad Zelck <git@simpel.cc>

README.md

 # Sort Lines
+
+With this tool you can sort newline separated lines alphabetically.
+
+![Screenshot des Tools](screenshot.png)
+
+You can either push the button "Paste, Sort & Copy" where the clipboard content is used as content or fill in your lines into textarea and push the button "Sort & Copy". In both cases the sorted result will be put back to clipboard.
+
+If you leave the default option "output unique lines only" set all lines existing more then once are deleted.
+
+There are two shortcuts to access the tool:
+* 1: Paste, Sort & Copy
+* 2: Sort & Copy