doc: fix minor formatting errors
doc: fix minor formatting errors

This patch does the following

 - Completes the backtick in `PropertyCallbackInfo`

 - Separates code from the explanation in "Method declaration" section

 - Aligns the parameters in the signatures to the first parameter

 - Separates two signatures with `;` so that they both will be Syntax highlighted.
gagern/nan,sesh-kebab/nan,ipmobiletech/nan,addaleax/nan,mikolalysenko/nan,eljefedelrodeodeljefe/nan,ipmobiletech/nan,addaleax/nan,sesh-kebab/nan,eljefedelrodeodeljefe/nan,nodejs/nan,gagern/nan,mikolalysenko/nan,mikolalysenko/nan,nodejs/nan,gagern/nan,nodejs/nan,eljefedelrodeodeljefe/nan,ipmobiletech/nan,sesh-kebab/nan,mikolalysenko/nan,addaleax/nan,addaleax/nan,ipmobiletech/nan,eljefedelrodeodeljefe/nan,nodejs/nan,sesh-kebab/nan