README.md: Fix MD040 warnings

The following warnings are generated by using markdownlint analysis:
```
MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
```
Refer to markdown-lint [1] to fix MD040
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/040-fenced-code-language.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I2242907114cff3e008e1aa4bce01d44079879b4b
diff --git a/README.md b/README.md
index bd975fa..8f37dcf 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 ## Building the Code
 
-```
+```text
 To build this package, do the following steps:
 
     1. meson build