fix style issue in put_tabs() widget

wang0618 · wang0618 · commit f056f1aca3a1 · 2021-10-31T23:05:24.000+08:00
reproduce code:
```
put_tabs([
        {'title': 'Text', 'content': 'Hello world'},
        {'title': 'Markdown', 'content': put_markdown('~~Strikethrough~~')},
    ]).style('height:500px')
```
diff --git a/pywebio/html/css/app.css b/pywebio/html/css/app.css
@@ -226,7 +226,8 @@ details[open]>summary {
     border-radius: .25rem;
     overflow: hidden;
     display: flex;
-    flex-wrap: wrap
+    flex-wrap: wrap;
+    align-content: flex-start;
 }
 
 .webio-tabs > label {

Original file line number	Diff line number	Diff line change
`@@ -226,7 +226,8 @@ details[open]>summary {`
`226`	`226`	`border-radius: .25rem;`
`227`	`227`	`overflow: hidden;`
`228`	`228`	`display: flex;`
`229`		`- flex-wrap: wrap`
	`229`	`+ flex-wrap: wrap;`
	`230`	`+ align-content: flex-start;`
`230`	`231`	`}`
`231`	`232`
`232`	`233`	`.webio-tabs > label {`