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: I839143a4afb1ebc7c7f08a2fccac85248b87218f
diff --git a/README.md b/README.md
index d8d480c..864e20e 100644
--- a/README.md
+++ b/README.md
@@ -2,9 +2,9 @@
 
 ## To Build
 
-```
 To build this package, do the following steps:
 
-    1. meson build
-    2. ninja -C build
+```sh
+1. meson build
+2. ninja -C build
 ```