Pages links point at docs.solidcraft.io: Flatpak repository, help and troubleshooting (#1922)

Thanks @CamWight.

crates/ui-egui/src/help.rs

@@ -11,7 +11,7 @@ pub const VERSION: &str = env!("CARGO_PKG_VERSION");
 pub const COMMIT: &str = env!("SOLIDCRAFT_COMMIT");
 pub const BUILD_DATE: &str = env!("SOLIDCRAFT_BUILD_DATE");
 /// The user and developer guide (docs/book, published by .github/workflows/pages.yml).
-pub const DOCS_URL: &str = "https://bherbruck.github.io/solidcraft/";
+pub const DOCS_URL: &str = "https://docs.solidcraft.io/";
 const ATTRIBUTION: &str = include_str!("../../../ATTRIBUTION.md");
 use solidcraft_engine::licences::{LICENSE_APACHE, LICENSE_MIT, NOTICE, THIRD_PARTY};
 /// Fonts: what this build carries.