Include downloadable KML of map (#30)

Include functionality to allow download of spatial circuit data as a KML file. Changes include:

    including button to download KML file
    updating all buttons in the GUI to make them more legible/useful
    adding documentation to documentation tab
    additional out_of_tool_processing tool to create voltage label KMLs from CSVs.

---------

Co-authored-by: Phoebe <[email protected]>

docs/documentation_tab.R

@@ -230,6 +230,12 @@ documentation_panel <- function() {
       Cleaned data is dispalyed if available else raw data is used. Be aware that the density of dots does not
       represent the density of pv systems, rather it represents the density of postcodes."
     ),
+    div(
+      "The chart is also available as a KML file, which can be imported into mapping programs (such as Google Earth).
+      A copy of the power lines data can be found here
+      (https://digital.atlas.gov.au/datasets/digitalatlas::electricity-transmission-lines/about).
+      To add voltage labels, follow the instructions in out_of_tool_processing/create_voltage_kml.R"
+    ),
     h4("Circuit count table"),
     div(
       "This table shows the number of circuits in each combination of the user specified grouping variables. Note for