add serde(alias = "exclude") to SingleProjectConfigFile

Summary:
In v12 the `relay-config` we were using `exclude` for this name.

Let's add an alias, so the migration from v12 to v13 is easier for configs that have `exclude` in them.

Reviewed By: voideanvalue

Differential Revision: D33378911

fbshipit-source-id: 106e071c414a25021953d00b96b92ae49e760cef

compiler/crates/relay-compiler/src/config.rs

@@ -562,6 +562,7 @@ pub struct SingleProjectConfigFile {
 
     /// Directories to ignore under src
     /// default: ['**/node_modules/**', '**/__mocks__/**', '**/__generated__/**'],
+    #[serde(alias = "exclude")]
     pub excludes: Vec<String>,
 
     /// List of directories with schema extensions.