DOC: explain run_server_side_script

Added the rtd theme as dependency and a docstring. I have the build docs here for you:

src/linkahead/utils/server_side_scripting.py

@@ -99,6 +99,19 @@ def _make_request(call, pos_args, opts, files=None):
 
 def run_server_side_script(call, *args, files=None, **kwargs):
     """
+    Parameters
+    ----------
+    call : str
+        name of the script to be called, potentially with path prefix (e.g. `management/update.py`)
+    *args : list(str)
+        list of positional arguments
+    files : dict
+        dictionary with where keys are the argument names with prefix (e.g. `-p1` or `-Ofile`) and
+        the values are the paths to the files to be uploaded. Note, that only the base name will be
+        used when uploaded. Files will be placed in the `.upload_files` folder. Thus, the script
+        will be called with the argument `<key>=.upload_files/<basename>`.
+    **kwargs : dict
+        kwargs will be passed to `_make_request`
 
     Return
     ------