Update to RGBDS 1.0 syntax and features

The tutorial has been written gradually over years by different authors, and in that time, RGBDS syntax has been through pretty many changes. Now that it's reached v1.0.0 the syntax is stable enough that I think it would be worth going through the code in the tutorial and ensuring that it's valid and idiomatic for the latest RGBDS.

(For example, [the Galactic Armada Makefile](https://github.com/gbdev/gb-asm-tutorial/blob/master/galactic-armada/Makefile) has `$(GFX) -c "#FFFFFF,#cfcfcf,#686868,#000000;"`, which would now idiomatically be `$(GFX) -c dmg`, and which could be enabling `-Weverything` warning diagnostics. The code itself might all still be simple enough -- no fancy macros or metaprogramming -- that nothing would need change, but the CLI usage at least could be improved.)

See also #125

チュートリアルのコードと Galactic Armada Makefile を RGBDS 1.0 の構文および CLI の規約に照らして確認し、Issue に記載された Makefile の例から始めます。関連するコンテキストとして issue #125 を使用し、その後、チュートリアルが引き続き有効で慣用的であること、またそのコマンドが古い使用方法に依存しなくなっていることを検証します。

索引モデルが issue の本文から書いたものです。