config.json: draw the base location markers again

[evertvorster]

base_locationmarker.spr is still in the pack and the engine still draws it at the centre of every hotspot -- the sprite the player is meant to see as they move the cursor towards a clickable area. The setting that names it was never carried into the JSON config, so it has been empty since the split, and the marker has not been drawn at all. Vega Strike 0.5.4's vegastrike.config named the sprite; the engine no longer reads the XML.

Sets graphics.bases.location_marker_sprite to base_locationmarker.spr, which is the value the old config used and what enable_location_markers and draw_location_text (both already true) were written to work with.

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Please answer the following:

Code Changes:

• Have the PR Validation Tests been run? See https://github.com/vegastrike/Vega-Strike-Engine-Source/wiki/Pull-Request-Validation
• This is a documentation change only

Issues:

• Please list any related issues

Purpose:

• What is this pull request trying to do?
• • Sets the config option to draw the base sprite.
• What release is this for?
• • 0.11
• Is there a project or milestone we should apply this to?
• • 0.11