ci(goreleaser): Install templ before generating templates

Adds a `go install` hook to `.goreleaser.yaml` to ensure the `templ` binary is
installed and up-to-date before `templ generate` is executed. This prevents
potential build failures in CI/CD environments where `templ` might not be
pre-installed or could be an outdated version, making the release process
more robust and self-contained.

.goreleaser.yaml

@@ -2,6 +2,7 @@ version: 2
 project_name: bilinovel-downloader
 before:
   hooks:
+    - go install github.com/a-h/templ/cmd/templ@latest
     - templ generate
 builds:
   - env: