Corrected MIR file path and fixed a typo (#1020)

Author: saki-osive

README.md

@@ -16,7 +16,7 @@ for the docs you're looking for instead of reading them top to bottom.
 
 ### Contributing to the guide
 
-The guide is useful today, but it has a lot of work still go.
+The guide is useful today, but it has a lot of work still to go.
 
 If you'd like to help improve the guide, we'd love to have you! You can find
 plenty of issues on the [issue

src/part-5-intro.md

@@ -9,7 +9,7 @@ and transform it into [MIR]. We have also shown how the compiler does various
 analyses on the code to detect things like type or lifetime errors. Now, we
 will finally take the MIR and produce some executable machine code.
 
-[MIR]: ./mir/index.html
+[MIR]: ./mir/index.md
 
 > NOTE: This part of a compiler is often called the _backend_ the term is a bit
 > overloaded because in the compiler source, it usually refers to the "codegen