Can't parse a pcb file generated from 5.0.2+dfsg1-1 (debian stable)

```
diff --git a/pykicad/pcb.py b/pykicad/pcb.py
index 18f437b..f28e648 100644
--- a/pykicad/pcb.py
+++ b/pykicad/pcb.py
@@ -454,7 +454,7 @@ class PcbPlotParams(AST):
'useauxorigin': boolean('useauxorigin'),
'hpglpennumber': integer,
'hpglpenspeed': integer,
- 'hpglpendiameter': integer,
+ 'hpglpendiameter': number,
'psnegative': boolean('psnegative'),
'psa4output': boolean('psa4output'),
'plotreference': boolean('plotreference'),
```

This is what the file looks like(snippet)
(mode 1)
(useauxorigin false)
(hpglpennumber 1)
(hpglpenspeed 20)
(hpglpendiameter 15.000000)
(psnegative false)
(psa4output false)
(plotreference true)
(plotvalue true)
(plotinvisibletext false)
(padsonsilk false)
(subtractmaskfromsilk false)

Start in pykicad/pcb.py at PcbPlotParams and inspect the hpglpendiameter parser entry. Use the provided pcb snippet as the reproduction case and verify that the file parses successfully, including the decimal value 15.000000.

Written by the indexing model from the issue text.