added documentation

README.md

@@ -66,7 +66,7 @@ fullscreen = true
 # Exit directly after copy/save action
 early-exit = true
 # Draw corners of rectangles round if the value is greater than 0 (0 disabled rounded corners)
-corner_roundness = 12,
+corner-roundness = 12
 # Select the tool on startup [possible values: pointer, crop, line, arrow, rectangle, text, marker, blur, brush]
 initial-tool = "brush"
 # Configure the command to be called on copy, for example `wl-copy`
@@ -117,6 +117,8 @@ Options:
           Filename to use for saving action. Omit to disable saving to file. Might contain format specifiers: <https://docs.rs/chrono/latest/chrono/format/strftime/index.html>
       --early-exit
           Exit directly after copy/save action
+      --corner-roundness <ROUNDNESS_FACTOR>
+          Draw corners of rectangles round if the value is greater than 0 (0 disabled rounded corners)
       --initial-tool <TOOL>
           Select the tool on startup [aliases: init-tool] [possible values: pointer, crop, line, arrow, rectangle, text, marker, blur, brush]
       --copy-command <COPY_COMMAND>