feat(leadspace): added ::part pseudo-element to component (#4752)

### Description

Added `::part` pseudo-element to `leadspace`

### Changelog

**New**

- `::part` pseudo element in `leadspace.ts`

packages/web-components/src/components/leadspace/leadspace.ts

@@ -24,6 +24,7 @@ const { stablePrefix: ddsPrefix } = ddsSettings;
  * The LeadSpace component.
  *
  * @element dds-leadspace
+ * @csspart section The first DOM node inside the shadow-root
  */
 @customElement(`${ddsPrefix}-leadspace`)
 class DDSLeadSpace extends StableSelectorMixin(LitElement) {
@@ -136,7 +137,7 @@ class DDSLeadSpace extends StableSelectorMixin(LitElement) {
   render() {
     const { gradientStyleScheme, type } = this;
     return html`
-      <section style="${this._getBackgroundImage()}" class="${this._getTypeClass()}">
+      <section style="${this._getBackgroundImage()}" class="${this._getTypeClass()}" part="section">
         <div class="${prefix}--leadspace__container">
           <div class="${this._getGradientClass()}">
             ${gradientStyleScheme === LEADSPACE_GRADIENT_STYLE_SCHEME.NONE

packages/web-components/tests/snapshots/dds-leadspace.md

@@ -7,6 +7,7 @@
 ```
 <section
   class="bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -45,6 +46,7 @@
 ```
 <section
   class="bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -85,6 +87,7 @@
 ```
 <section
   class="bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -123,6 +126,7 @@
 ```
 <section
   class="bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -163,6 +167,7 @@
 ```
 <section
   class="bx--leadspace--centered bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -208,6 +213,7 @@
 ```
 <section
   class="bx--leadspace--centered bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -255,6 +261,7 @@
 ```
 <section
   class="bx--leadspace--centered bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -300,6 +307,7 @@
 ```
 <section
   class="bx--leadspace--centered bx--leadspace--centered__image bx--leadspace__section"
+  part="section"
   style="background-image: url(http://fpoimg.com/1056x480?bg_color=ee5396&text_color=161616)"
 >
   <div class="bx--leadspace__container">
@@ -347,6 +355,7 @@
 ```
 <section
   class="bx--leadspace--productive bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -385,6 +394,7 @@
 ```
 <section
   class="bx--leadspace--productive bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -425,6 +435,7 @@
 ```
 <section
   class="bx--leadspace--productive bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">
@@ -463,6 +474,7 @@
 ```
 <section
   class="bx--leadspace--productive bx--leadspace__section"
+  part="section"
   style=""
 >
   <div class="bx--leadspace__container">