fix: provide lsp4j source bundles on p2 update site

Fixes #1519

Author: iloveeclipse

pom.xml

@@ -202,6 +202,14 @@
 						</baselineRepositories>
 					</configuration>
 				</plugin>
+				<plugin>
+					<groupId>org.eclipse.tycho</groupId>
+					<artifactId>tycho-p2-repository-plugin</artifactId>
+					<version>${tycho-version}</version>
+					<configuration>
+						<includeAllSources>true</includeAllSources>
+					</configuration>
+				</plugin>
 			</plugins>
 		</pluginManagement>
 	</build>