Generate labels with pangocairo (#8)

Goal of this PR is to have some basic labels generated with pangocairo
- size of the canvas should be matching the input text and grow/shrink accordingly
- basic formatting options like fontsize and align should be working

Reviewed-on: moritz/ptouch-prnt#8

meson_options.txt

@@ -0,0 +1,4 @@
+option('usb_trace_only',
+  type: 'boolean',
+  value: false,
+  description: 'Enable USB trace mode: log USB data without sending to device (saves label tape during debugging)')