Change bold text to headings to add id for links

CONTRIBUTING.md

@@ -34,21 +34,21 @@ When writing step-by-step instructions (e.g. how to install something), try to f
 
 ### Syntax
 
-**Prefer JSX to `createElement`.**
+#### Prefer JSX to `createElement`.
 
 Ignore this if you're specifically describing `createElement`.
 
-**Use `const` where possible, otherwise `let`. Don't use `var`.**
+#### Use `const` where possible, otherwise `let`. Don't use `var`.
 
 Ignore this if you're specifically writing about ES5.
 
-**Don't use ES6 features when equivalent ES5 features have no downsides.**
+#### Don't use ES6 features when equivalent ES5 features have no downsides.
 
 Remember that ES6 is still new to a lot of people. While we use it in many places (`const` / `let`, classes, arrow functions), if the equivalent ES5 code is just as straightforward and readable, consider using it.
 
 In particular, you should prefer named `function` declarations over `const myFunction = () => ...` arrows for top-level functions. However, you *should* use arrow functions where they provide a tangible improvement (such as preserving `this` context inside a component). Consider both sides of the tradeoff when deciding whether to use a new feature.
 
-**Don't use features that aren't standardized yet.**
+#### Don't use features that aren't standardized yet.
 
 For example, **don't** write this: