feat(button): support large size button

Set size to "lg" to use the large size.

docs/src/COMPONENT_API.json

@@ -362,7 +362,7 @@
           "name": "size",
           "kind": "let",
           "description": "Specify the size of button",
-          "type": "\"default\" | \"field\" | \"small\" | \"xl\"",
+          "type": "\"default\" | \"field\" | \"small\" | \"lg\" | \"xl\"",
           "value": "\"default\"",
           "isFunction": false,
           "constant": false,

docs/src/pages/components/Button.svx

@@ -78,7 +78,7 @@ If an `href` value is specified, the component will render an [anchor element](h
   <p {...props}>Custom element</p>
 </Button>
 
-### Field button
+### Field size
 
 <Button size="field">Primary</Button>
 <Button size="field" kind="secondary">Secondary</Button>
@@ -86,7 +86,7 @@ If an `href` value is specified, the component will render an [anchor element](h
 <Button size="field" kind="ghost">Ghost</Button>
 <Button size="field" kind="danger">Danger</Button>
 
-### Small button
+### Small size
 
 <Button size="small">Primary</Button>
 <Button size="small" kind="secondary">Secondary</Button>
@@ -94,7 +94,15 @@ If an `href` value is specified, the component will render an [anchor element](h
 <Button size="small" kind="ghost">Ghost</Button>
 <Button size="small" kind="danger">Danger</Button>
 
-### Extra-large button
+### Large size
+
+<Button size="lg">Primary</Button>
+<Button size="lg" kind="secondary">Secondary</Button>
+<Button size="lg" kind="tertiary">Tertiary</Button>
+<Button size="lg" kind="ghost">Ghost</Button>
+<Button size="lg" kind="danger">Danger</Button>
+
+### Extra-large size
 
 <Button size="xl">Primary</Button>
 <Button size="xl" kind="secondary">Secondary</Button>