website: docs for data dir missing

Author: Kade-N

docs/_common-errors/data-directory-missing.md

@@ -0,0 +1,14 @@
+---
+title: Data directory is missing or corrupt
+---
+You may also see "Configuration Script Failed" along with this error. The two errors are related.
+
+## Steam users
+Please launch Spore Galactic Adventures once from Steam before using the Launcher Kit. Afterwards, you should always use the ModAPI Launcher instead of launching from Steam.
+
+The error happens because Steam does not finish installing games until the first time they are launched. As a result, the game cannot start because it is not fully installed, and the Launcher Kit is unable to detect that the game is installed.
+
+This also eliminates an issue where you may be prompted to choose where the game is installed when using the Launcher kit. You should not continue to receive this prompt.
+
+## All other users
+Please [ask for help](/support).