docs: Match Single Blank Line Above and Below A Title

Signed-off-by: Yifei Ding <yifeiding@protonmail.com>

docs/HallFilamentWidthSensor.md

@@ -5,6 +5,7 @@ This document describes Filament Width Sensor host module. Hardware used for dev
 [Hall based filament width sensor assembly video](https://www.youtube.com/watch?v=TDO9tME8vp4)
 
 ## How does it work?
+
 Sensor generates two analog output based on calculated filament width. Sum of output voltage always equals to detected filament width . Host module monitors voltage changes and adjusts extrusion multiplier. I use aux2 connector on ramps-like board analog11 and analog12 pins. You can use different pins and differenr boards
 
 ## Configuration
@@ -71,6 +72,7 @@ Sensor generates two analog output based on calculated filament width. Sum of ou
 
 
 ## Commands
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 **QUERY_FILAMENT_WIDTH** - Return the current measured filament width as result
 
 **RESET_FILAMENT_WIDTH_SENSOR** – Clear all sensor readings. Can be used after filament change.
@@ -107,6 +109,7 @@ Sensor generates two analog output based on calculated filament width. Sum of ou
     index: 1
 
 ## Calibration procedure
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 Insert first  calibration rod (1.5 mm size) get first  raw sensor value
 
 To get raw sensor value you can use menu item or  **QUERY_RAW_FILAMENT_WIDTH** command in terminal
@@ -116,9 +119,11 @@ Insert second calibration rod (2.0 mm size) get second raw sensor value
 Save raw values in config
 
 ## How to enable sensor
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 After power on by default sensor disabled.
 Enable sensor in start g-code by command **ENABLE_FILAMENT_WIDTH_SENSOR** or change enable parameter in config
 
 ## Logging
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 After power on by default diameter Logging disabled.
 Data to log added on every measurement interval (10 mm by default)