Add link to developer guide (#969)

* Add link to developer guide

* Update buildSrc/src/main/kotlin/DocsLandingPage.kt

Co-authored-by: John DiSanti <jdisanti@amazon.com>

Co-authored-by: John DiSanti <jdisanti@amazon.com>

buildSrc/src/main/kotlin/DocsLandingPage.kt

@@ -19,8 +19,9 @@ fun Project.docsLandingPage(awsServices: List<AwsService>, outputDir: File) {
     with(writer) {
         write("# AWS SDK for Rust")
         write(
-            """The AWS SDK for Rust contains one crate for each AWS service, as well as ${cratesIo("aws-config")} ${docsRs("aws-config")},
-            |a crate implementing configuration loading such as credential providers.""".trimMargin()
+            "The AWS SDK for Rust contains one crate for each AWS service, as well as ${cratesIo("aws-config")} " +
+                "${docsRs("aws-config")}, a crate implementing configuration loading such as credential providers. " +
+                "For usage documentation see the [Developer Guide](https://docs.aws.amazon.com/sdk-for-rust/latest/dg/welcome.html)."
         )
 
         writer.write("## AWS Services")