Change font size settings to pixels

WebKit only accepts integer px. So it would be hard to control if the
settings are in fractional pt.

Also change max size settings to uint, as they currently don't support
-1.

data/com.github.johnfactotum.Foliate.gschema.xml

@@ -61,13 +61,13 @@
     <key name="gap" type="d">
       <default>0.06</default>
     </key>
-    <key name="max-inline-size" type="i">
+    <key name="max-inline-size" type="u">
       <default>720</default>
     </key>
-    <key name="max-block-size" type="i">
+    <key name="max-block-size" type="u">
       <default>1440</default>
     </key>
-    <key name="max-column-count" type="i">
+    <key name="max-column-count" type="u">
       <default>2</default>
     </key>
     <key name="scrolled" type="b">
@@ -92,10 +92,10 @@
     <key name="default" type="u">
       <default>0</default>
     </key>
-    <key name="default-size" type="d">
-      <default>12</default>
+    <key name="default-size" type="u">
+      <default>16</default>
     </key>
-    <key name="minimum-size" type="d">
+    <key name="minimum-size" type="u">
       <default>0</default>
     </key>
   </schema>

src/book-viewer.js

@@ -237,7 +237,7 @@ GObject.registerClass({
         'sans-serif': 'Sans 12',
         'monospace': 'Monospace 12',
         'default': 'serif',
-        'default-size': 12,
+        'default-size': 16,
     })
     viewSettings = new ViewSettings({
         'brightness': 1,
@@ -341,9 +341,9 @@ GObject.registerClass({
             monospace_font_family: getFamily(font.monospace),
             default_font_family: getFamily(font.default === 1
                 ? font.sans_serif : font.serif),
-            default_font_size: WebKit.Settings.font_size_to_pixels(font.default_size),
+            default_font_size: font.default_size,
             // TODO: disable this for fixed-layout
-            minimum_font_size: WebKit.Settings.font_size_to_pixels(font.minimum_size),
+            minimum_font_size: font.minimum_size,
         })
         const view = this.viewSettings
         if (this.#bookReady) await this.#exec('reader.setAppearance', {