Add syntax highlighting to MIR.md
## MIR API example
* The following code on C creates MIR analog of C code
`int64_t loop (int64_t arg1) {int64_t count = 0; while (count < arg1) count++; return count;}`
-```
+```c
MIR_module_t m = MIR_new_module (ctx, "m");
MIR_item_t func = MIR_new_func (ctx, "loop", MIR_T_I64, 1, MIR_T_I64, "arg1");
MIR_reg_t COUNT = MIR_new_func_reg (ctx, func->u.func, MIR_T_I64, "count");
* Sieve of eratosthenes:
-```
+```mir
m_sieve: module
export sieve
sieve: func i32, i32:N
@@ -487,7 +487,7 @@ ex100: func v
* Example of block arguments and `va_stack_arg`
-```
+```mir
m0: module
f_p: proto i64, 16:blk(a), ...
f: func i64, 16:blk(a), ...
