doc: readme: add microblaze to toolchains list

Author: alpsayin

README.md

@@ -8,6 +8,7 @@ The toolchains for the following target architectures are supported:
 
 - ARC (32-bit and 64-bit; ARCv1, ARCv2, ARCv3)
 - ARM (32-bit and 64-bit; ARMv6, ARMv7, ARMv8; A/R/M Profiles)
+- Microblaze (32-bit)
 - MIPS (32-bit and 64-bit)
 - Nios II
 - RISC-V (32-bit and 64-bit; RV32I, RV32E, RV64I)