Add white backgrounds to SVGs

docs/img/contact_printer.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="297mm" version="1.1" viewBox="347.376621 189.71561485 1256.373958 888.4358702999999" width="420mm">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 361.1012,477.696 L 362.7258,476.9701" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 364.5475,476.279 L 366.5459,475.6299 L 368.6993,475.0298 L 370.984,474.4849 L 373.3753,474.0007 L 375.8477,473.5824 L 427.9105,465.5999" fill="none" stroke="black" stroke-width="1.0"/>

docs/img/contact_printer_frame.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="870px" version="1.1" width="1910px">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 316.8719,388.9917 L 506.4295,185.354" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 519.6448,184.7417 L 507.8785,184.7417 L 318.895,388.1618 L 335.6346,388.1618" fill="none" stroke="black" stroke-width="1.0"/>

docs/img/contact_printer_gate_comparison.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="1050px" version="1.1" width="1270px">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 88.9226,250.2137 L 93.3916,291.2128" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 93.3916,291.2128 L 166.2751,959.8525 L 180.5345,985.5164 L 112.2855,343.6026 L 129.8731,358.2288" fill="none" stroke="black" stroke-width="1.0"/>

docs/img/contact_printer_gates.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="670px" version="1.1" width="1910px">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 416.9363,238.8175 L 456.3745,464.6573 L 459.7783,465.2483 L 457.6185,452.7984 L 465.6656,454.0462 L 467.7928,466.5047 L 475.9265,467.646" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 467.7928,466.5047 L 459.7783,465.2483" fill="none" stroke="black" stroke-width="1.0"/>

docs/img/contact_printer_sprocketed_roller_invert_solid.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="1050px" version="1.1" width="1070px">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 74.6819,383.4154 L 76.4977,391.1229" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 80.3694,398.904 L 86.3757,406.7218" fill="none" stroke="black" stroke-width="1.0"/>

docs/img/contact_printer_takeup.svg

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink" baseProfile="full" height="1050px" version="1.1" width="790px">
+  <style>svg { background-color: white; }</style>
   <defs/>
   <path d="M 385.3332,125.7754 L 385.3902,156.0548" fill="none" stroke="black" stroke-width="1.0"/>
   <path d="M 387.9943,157.6277 L 387.9507,125.8421" fill="none" stroke="black" stroke-width="1.0"/>