docs(java): Add SoftAssertions for Java (#26512)

This PR adds the `SoftAssertions` API for Java. Related PR:
microsoft/playwright-java#1340

Note: microsoft/playwright.dev#1135 needs to be
merged in order for the markdown in this PR to be rendered without
errors

docs/src/api/class-softassertions.md

@@ -0,0 +1,115 @@
+# class: SoftAssertions
+* since: v1.38
+* langs: java
+
+The [SoftAssertions] class provides assertion methods that can be used to make multiple assertions without failing the test immediately.
+
+```java
+...
+import com.microsoft.playwright.assertions.SoftAssertions;
+
+public class TestPage {
+  ...
+  @Test
+  void hasUrlTextPass() {
+    SoftAssertions softly = SoftAssertions.create();
+    page.getByText("Sign in").click();
+    softly.assertThat(page).hasURL(Pattern.compile(".*/login"));
+    softly.assertAll();
+  }
+}
+```
+
+## method: SoftAssertions.create
+* since: v1.38
+* langs: java
+- returns: <[SoftAssertions]>
+
+Creates a [SoftAssertions] object.
+
+**Usage**
+
+```java
+SoftAssertions softly = SoftAssertions.create();
+```
+
+## method: SoftAssertions.expectLocator
+* since: v1.38
+* langs:
+  - alias-java: assertThat(locator)
+- returns: <[LocatorAssertions]>
+
+Creates a [LocatorAssertions] object for the given [Locator].
+
+**Usage**
+
+```java
+SoftAssertions softly = SoftAssertions.create();
+...
+softly.assertThat(locator).isVisible();
+```
+
+### param: SoftAssertions.expectLocator.locator
+* since: v1.38
+- `locator` <[Locator]>
+
+[Locator] object to use for assertions.
+
+## method: SoftAssertions.expectPage
+* since: v1.38
+* langs:
+  - alias-java: assertThat(page)
+- returns: <[PageAssertions]>
+
+Creates a [PageAssertions] object for the given [Page].
+
+**Usage**
+
+```java
+SoftAssertions softly = SoftAssertions.create();
+...
+softly.assertThat(page).hasTitle("News");
+```
+
+### param: SoftAssertions.expectPage.page
+* since: v1.38
+- `page` <[Page]>
+
+[Page] object to use for assertions.
+
+## method: SoftAssertions.expectAPIResponse
+* since: v1.38
+* langs:
+  - alias-java: assertThat(response)
+
+- returns: <[APIResponseAssertions]>
+
+Creates a [APIResponseAssertions] object for the given [APIResponse].
+
+**Usage**
+
+```java
+SoftAssertions softly = SoftAssertions.create();
+...
+softly.assertThat(response).isOK();
+```
+
+### param: SoftAssertions.expectAPIResponse.response
+* since: v1.38
+- `response` <[APIResponse]>
+
+[APIResponse] object to use for assertions.
+
+## method: SoftAssertions.assertAll
+* since: v1.38
+* langs: java
+
+Runs all the assertions have been executed for this [SoftAssertions] object.  If any assertions fail, this method throws an AssertionFailedError with the details of all the failed assertions.
+
+**Usage**
+
+```java
+SoftAssertions softly = SoftAssertions.create();
+...
+softly.assertAll();
+```