More templates

[jonringer]

- Added `php` template for Composer-based PHP projects using buildComposerProject2
- Added `maven` template for Maven-based Java projects using buildMavenPackage
- Added `elixir` template for Mix-based Elixir applications using mixRelease/buildMix
- Added `gradle` template for Gradle-based Java/Kotlin projects using gradle.fetchDeps
- Added `dart` template for Dart applications using buildDartApplication
- Added `haskell` template for Haskell packages using haskellPackages.callCabal2nix
- Added `ocaml` template for OCaml packages using buildDunePackage
- Added `scala` template for Scala/SBT packages using stdenv.mkDerivation with sbt-derivation
- Added `clojure` template for Clojure projects using deps.edn or Leiningen with clj-nix
- Added `perl` template for Perl modules using buildPerlPackage or buildPerlModule
- Added `lua` template for Lua packages and applications using buildLuaPackage or buildLuaApplication
- Added `r` template for R packages using rPackages.buildRPackage