Add note about autodetection of RCT1 installs

Author: Gymnasiast

installing/installing-on-linux-bsd.rst

@@ -216,6 +216,8 @@ Once this is done, you can now start OpenRCT2. You will be asked to provide the
 Getting the RCT1 files (optional, but recommended)
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+Depending on your situation, your RCT1 install may be autodetected. If not, you will have provide a location manually.
+
 Extracting the RCT1 files works much the same way as those from RCT2.
 
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