Add fname to plot_network to specify output filename.

plot_network() is used to plot various types of networks. However, the name of the produced html-file was hard-coded to "citation.html". This change introduces a fname-parameter, that allows to specify other file-names. It defaults to "citation.html" to keep compability with previous versions.

litstudy/network.py

@@ -40,7 +40,8 @@ def plot_network(
     controls=False,
     scale=1,
     iterations=1000,
-    gravity=1
+    gravity=1,
+    fname='citation.html'
 ):
     """Plot a `networkx.Graph` generated by one of the `build_X_graph`
     functions in this module. Plotting is done using the `pyvis` library.
@@ -152,7 +153,7 @@ def plot_network(
         )
     )
 
-    return v.show("citation.html")
+    return v.show(fname)
 
 
 def build_base_network(