reduce min file read delay to 2 ms

Author: semuadmin

README.md

@@ -106,7 +106,7 @@ For more comprehensive installation instructions, please refer to [INSTALLATION.
 1. To connect to a TCP or UDP socket, enter the server URL and port, select the protocol (defaults to TCP) and click 
 ![connect socket icon](https://github.com/semuconsulting/PyGPSClient/blob/master/src/pygpsclient/resources/ethernet-1-24.png?raw=true). For encrypted TLS connections, tick the 'TLS' checkbox. Tick the 'Self Sign' checkbox to accommodate self-signed TLS certification (*typically for test or demonstration services*).
 1. To stream from a previously-saved <a name="filestream">binary datalog file</a>, click 
-![connect-file icon](https://github.com/semuconsulting/PyGPSClient/blob/master/src/pygpsclient/resources/binary-1-24.png?raw=true) and select the file type (`*.log, *.ubx, *.*`) and path. PyGPSClient datalog files will be named e.g. `pygpsdata-20220427114802.log`, but any binary dump of an GNSS receiver output is acceptable, including `*.ubx` files produced by u-center.
+![connect-file icon](https://github.com/semuconsulting/PyGPSClient/blob/master/src/pygpsclient/resources/binary-1-24.png?raw=true) and select the file type (`*.log, *.ubx, *.*`) and path. PyGPSClient datalog files will be named e.g. `pygpsdata-20220427114802.log`, but any binary dump of an GNSS receiver output is acceptable, including `*.ubx` files produced by u-center. The 'File Delay' spinbox sets the delay in milliseconds between individual file reads, acting as a throttle on file readback.
 1. To disconnect from the data stream, click
 ![disconnect icon](https://github.com/semuconsulting/PyGPSClient/blob/master/src/pygpsclient/resources/iconmonstr-media-control-50-24.png?raw=true).
 1. To exit the application, click

src/pygpsclient/settings_frame.py

@@ -115,7 +115,7 @@
 )
 
 MAXLINES = ("200", "500", "1000", "2000", "100")
-FILEDELAYS = (10, 20, 50, 100, 200, 500, 1000, 2000)
+FILEDELAYS = (2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000)
 # initial dimensions adjusted for different widget
 # rendering on different platforms
 if system() == "Linux":  # Wayland