Documentation updates

docs/api/custom-platform.md

@@ -24,7 +24,7 @@ Every platform is defined in an `.ini` file with an appropriate name.
     
     * `65816` (WDC 65816/65802; experimental; currently only programs that use only 16-bit addressing are supported)
     
-    * `z80` (Zilog Z80; experimental and very incomplete)
+    * `z80` (Zilog Z80; experimental and slightly incomplete)
 
 * `encoding` – default encoding for console I/O, one of 
 `ascii`, `pet`/`petscii`, `petscr`/`cbmscr`, `atascii`, `bbc`, `jis`/`jisx`, `apple2`,

docs/api/target-platforms.md

@@ -2,7 +2,8 @@
                                                       
 # Target platforms
 
-Currently, Millfork supports creating disk- or tape-based programs for Commodore, Apple, BBC and Atari 8-bit computers
+Currently, Millfork supports creating disk- or tape-based programs
+for Commodore, Apple, BBC and Atari 8-bit computers, NEC PC-88, ZX Spectrum 48k,
 and cartridge-based programs for Famicom/NES and Atari 2600,
 but it may be expanded to support other 6502-based and Z80-based platforms in the future.
 
@@ -54,9 +55,9 @@ Read [the BBC Micro programming guide](./bbcmicro-programming-guide.md) for more
 The compiler only emits raw binaries, not disk images.
 Read [the Apple 2 programming guide](./apple2-programming-guide.md) for more info.
 
-* `pc88` – NEC PC-88 (very incomplete and not usable for anything yet)
+* `pc88` – NEC PC-88 (no ROM routines are mapped yet)
 
-* `zxspectrum` – Sinclair ZX Spectrum 48k (very incomplete and not usable for anything yet)
+* `zxspectrum` – Sinclair ZX Spectrum 48k
 
 The primary and most tested platform is Commodore 64.