docs: add gcp informations

README.md

@@ -26,8 +26,9 @@ Then add the parameters:
 | -skip | Number of lines to be skipped before reading the file (optional) |
 | -w | Worksite output file format ex:opk |
 | -pr | Conversion path ex:test/tmp/ |
-| -c | Files paths of cameras (xml or txt) |
+| -c | Files paths of cameras (.xml or .txt) |
 | -cp | Files paths of connecting points (.mes) |
+| -gcp | Files paths of ground control point (.app) |
 
 Some settings are optional, depending on what you want to do with Pink Lady.
 
@@ -42,3 +43,4 @@ Html documentation in docs/_build/html/index.hmlt
       - function : def read(file: str) -> Worksite:
 3. Reading a camera file (XML and txt)
 4. Reading connecting point (mes)
+5. Reading ground control point (app)