add part about GPIB

Author: LilyTronics

docs/introduction.rst

@@ -21,3 +21,13 @@ Features
 * Adding your own instrument drivers (see manual)
 * Data from the table can be copied and pasted to a spreadsheet (Excel, LibreOffice, etc.).
 * Export to CSV for using data in other applications (databases, scripting, etc.).
+
+About GPIB...
+-------------
+
+We get some questions if GPIB will be supported. GPIB is a standarized communication bus for instruments. But the standardization is only on the GPIB part.
+The command and response structure are standarized. What is not standarized is the GPIB PC controller. In the past PCs used ISA cards.
+Now a days you need to have a USB to GPIB controller. And in this controller lies the problem. Supporting the GPIB protocol is fairly easy.
+Supporting all available GPIB controllers on the market is a headache. Every GPIB controller requires its own specific driver.
+And to test it, we need a sample of each controller available. And those controllers are not cheap. So for now it is not very feasible to have GPIB supported.
+But... if someone is willing to donate a GPIB controller, we will be happy to add support for it.