Allow to print custom amount of lines before and after the provided location

[kamilkisiela]

[IvanGoncharov]

@kamilkisiela Can you please describe the purpose?

[kamilkisiela]

We use it internally to print a location of an error but the default 1 line before and after is not that helpful.

schema.graphql:2783:9
    2782 |           
    2783 |         }
         |         ^
    2784 |

schema.graphql:2783:9
    2780 |       
    2781 |         input BatchInput {
    2782 |           
    2783 |         }
         |         ^
    2784 |         
    2785 |       
    2786 |         type SingleInput {

I don't mind applying this change only to the lines "before" the actual line of an error.

schema.graphql:2783:9
    2781 |         input BatchInput {
    2782 |           
    2783 |         }
         |         ^
    2784 |         

I think even changing the default to 2 lines instead of 1 is also acceptable on my side (I can prepare another PR).

[IvanGoncharov]

@kamilkisiela Thanks for the explanation 👍 Makes sense. Quick question why do you point to the end of the node and not to the beginning of the node?

[IvanGoncharov]

@kamilkisiela I missed that it's an empty type so you probably get this error from the parser. Do you use printSourceLocation directly or you are using GraphQLError.toString?