docs: update architecture list

docs/introduction.txt

@@ -23,10 +23,10 @@ GNU libc and newlib.
 Embedded systems often use processors that are not the regular x86
 processors everyone is used to having in his PC. 
 
-OpenADK supports 38 different architectures:
+OpenADK supports 40 different architectures:
 AARCH64, Alpha, ARC, ARM, AVR32, Blackfin, C6X, CR16, CRIS, Epiphany, FR-V,
 H8/300, HPPA, IA64, LM32, M32R, M68K, METAG, Microblaze, MIPS, MIPS64, MN10300,
-Moxie, MSP430, NDS32, NIOS2, OR1K, PPC, PPC64, S/390, SH, SPARC, SPARC64, Tile,
+Moxie, MSP430, NDS32, NIOS2, OR1K, PPC, PPC64, RiscV, RX, S/390, SH, SPARC, SPARC64, Tile,
 V850, X86, X86_64 and Xtensa.
 
 OpenADK supports numerous processors and their variants; it also comes