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

tests/meson.build

@@ -5,9 +5,9 @@ tests = [
         ['../src/graphics/Bitmap.cpp', 'bitmap_test/bitmap_test.cpp'],
     ],
     [
-        'image_test',
-        'image_test_exe',
-        ['../src/graphics/Image.cpp', 'image_test/image_test.cpp'],
+        'label_test',
+        'label_test_exe',
+        ['../src/graphics/Label.cpp', 'label_test/label_test.cpp'],
     ],
     [
         'monochrome_test',
@@ -36,3 +36,5 @@ foreach test : tests
         ),
     )
 endforeach
+
+