Include imported Still Alive data with disclaimer

Commit src/still_alive/imported.h instead of ignoring it. The importer now
writes a source reference (SDSkyKlouD/still-alive-web) and a disclaimer
(Jonathan Coulton / Valve, personal non-commercial use, not affiliated) at
the top of the file; the README carries the same disclaimer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -24,6 +24,3 @@ $RECYCLE.BIN/
 # Editors
 *.swp
 *~
-
-# Imported still_alive text (tools/import_still_alive.py)
-src/still_alive/imported.h