Documentation correction (#665)

Readability.

src/README.md

@@ -4,13 +4,13 @@ Header files in include are public APIs that share across modules.
 There can be internal header files within each module that sit in src.
 
 ## Modules
-- common Internal common utilities.
-- api API function registration
-- lang The definition of DSL related data structure
-- arithmetic Arithmetic expression and set simplification
-- op The detail implementations about each operation(compute, scan, placeholder)
-- schedule The operations on the schedule graph before converting to IR.
-- pass The optimization pass on the IR structure
-- codegen The code generator.
-- runtime Minimum runtime related codes
-- contrib Contrib extension libraries
+- common: Internal common utilities.
+- api: API function registration
+- lang: The definition of DSL related data structure
+- arithmetic: Arithmetic expression and set simplification
+- op: The detail implementations about each operation(compute, scan, placeholder)
+- schedule: The operations on the schedule graph before converting to IR.
+- pass: The optimization pass on the IR structure
+- codegen: The code generator.
+- runtime: Minimum runtime related codes
+- contrib: Contrib extension libraries