Add gradle.lockfile to Dependabot supported files documentation (#58815)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: felickz <1760475+felickz@users.noreply.github.com>
Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: 3 people

data/reusables/dependabot/supported-package-managers.md

@@ -117,6 +117,7 @@ For more information about using {% data variables.product.prodname_dependabot_v
 {% data variables.product.prodname_dependabot %} doesn't run Gradle but supports updates to the following files:
 * `build.gradle`, `build.gradle.kts` (for Kotlin projects)
 * `gradle/libs.versions.toml` (for projects using a standard Gradle version catalog)
+* `gradle.lockfile` (for projects using Gradle dependency locking)
 * Files included via the `apply` declaration that have `dependencies` in the filename. Note that `apply` does not support `apply to`, recursion, or advanced syntaxes (for example, Kotlin's `apply` with `mapOf`, filenames defined by property).
 
 {% data variables.product.prodname_dependabot %} uses information from the `pom.xml` file of dependencies to add links to release information in update pull requests. If the information is omitted from the `pom.xml` file, then it cannot be included in {% data variables.product.prodname_dependabot %} pull requests, see [AUTOTITLE](/code-security/dependabot/ecosystems-supported-by-dependabot/optimizing-java-packages-dependabot).