fix static-files readme name

middleware/middleware-ext-mut/README.md

@@ -4,7 +4,7 @@ This example showcases a middleware that adds and retrieves request-local data.
 
 ## Usage
 
-```bash
+```sh
 cd middleware/middleware-ext-mut
 cargo run
 ```

middleware/middleware-http-to-https/README.md

@@ -8,7 +8,7 @@ Now, the only problem left to solve is, to listen to **HTTP** connections as wel
 
 ## Usage
 
-```bash
+```sh
 cd middleware/middleware-http-to-https
 cargo run
 ```

middleware/middleware/README.md

@@ -4,7 +4,7 @@ This example showcases a bunch of different uses of middleware. See also the [Mi
 
 ## Usage
 
-```bash
+```sh
 cd basics/middleware
 cargo run
 # Started http server: 127.0.0.1:8080