Add line breaks before/after code blocks (#291)

Author: catamorphism

component-model/src/design/why-component-model.md

@@ -22,12 +22,15 @@ binary `.wasm` file.
 
 A core module usually corresponds to a single binary `.wasm` file.
 Here's what the `file` command outputs for a sample `.wasm` file:
+
 ```console
 $ file adder.wasm
 adder.wasm: WebAssembly (wasm) binary module version 0x1 (MVP)
 ```
+
 The file can also be inspected
 using [the `wasm-tools` CLI](https://github.com/bytecodealliance/wasm-tools):
+
 ```console
 $ wasm-tools print adder.wasm | head -1
 (module
@@ -151,12 +154,15 @@ Conceptually, a component is a WebAssembly binary
 that is restricted to interact
 only through the modules' imported and exported functions.
 Components use a different binary format:
+
 ```console
 $ file add.component.wasm
 add.component.wasm: WebAssembly (wasm) binary module version 0x1000d
 ```
+
 Inspecting the file with the `wasm-tools` CLI
 shows more clearly that it contains a component:
+
 ```
 $ wasm-tools print add.component.wasm | head -1
 (component