fix(popselect): default placement & padding

CHANGELOG.en-US.md

@@ -15,6 +15,7 @@
 - Fix `n-description`'s warning caused by `v-if` that should not appear, closes [#1083](https://github.com/TuSimple/naive-ui/issues/1083).
 - Fix `n-layout`'s `sider-placement` doesn't work after build, closes [#978](https://github.com/TuSimple/naive-ui/issues/978).
 - Fix `n-input-number`'s `step` calculate error when the value is decimal, closes [#1007](https://github.com/TuSimple/naive-ui/issues/1007).
+- Fix `n-popselect`' s default placement and padding.
 
 ### Feats
 

CHANGELOG.zh-CN.md

@@ -15,6 +15,7 @@
 - 修复 `n-description` 中因 `v-if` 导致的不该出现的警告，关闭 [#1083](https://github.com/TuSimple/naive-ui/issues/1083)
 - 修复 `n-layout` 的 `sider-placement` 属性在打包之后不生效，关闭 [#978](https://github.com/TuSimple/naive-ui/issues/978)
 - 修复 `n-input-number` 的 `step` 值为小数时计算错误，关闭 [#1007](https://github.com/TuSimple/naive-ui/issues/1007)
+- 修复 `n-popselect` 的默认位置和 padding
 
 ### Feats
 

src/popselect/src/Popselect.tsx

@@ -15,6 +15,10 @@ import { popselectInjectionKey } from './interface'
 const popselectProps = {
   ...(useTheme.props as ThemeProps<PopselectTheme>),
   ...popoverBaseProps,
+  placement: {
+    ...popoverBaseProps.placement,
+    default: 'bottom'
+  },
   trigger: {
     type: String as PropType<PopoverTrigger>,
     default: 'hover'
@@ -58,6 +62,9 @@ export default defineComponent({
     const popoverProps: PopoverInternalProps & { ref: string } = {
       theme: mergedTheme.peers.Popover,
       themeOverrides: mergedTheme.peerOverrides.Popover,
+      builtinThemeOverrides: {
+        padding: '0'
+      },
       ref: 'popoverInstRef',
       internalRenderBody: (
         className,