update README.md adding note for preprocess must be sync function

NicoCevallos · NicoCevallos · commit 1d03152cc4e1 · 2021-02-16T14:41:58.000-03:00
diff --git a/README.md b/README.md
@@ -110,6 +110,7 @@ You can use a preprocessor function to return custom AST info according to the o
 
 For now this only supports `module` and `instance` scripts.
 
+NOTE: The preprocess function MUST be a synchronous function because ESLint works doesn't work with async functions. See issue [#10 (comment)](https://github.com/sveltejs/eslint-plugin-svelte3/issues/10#issuecomment-490634346)
 
 ## Using the CLI
 

Original file line number	Diff line number	Diff line change
`@@ -110,6 +110,7 @@ You can use a preprocessor function to return custom AST info according to the o`
`110`	`110`
`111`	`111`	For now this only supports `module` and `instance` scripts.
`112`	`112`
	`113`	`+NOTE: The preprocess function MUST be a synchronous function because ESLint works doesn't work with async functions. See issue [#10 (comment)](https://github.com/sveltejs/eslint-plugin-svelte3/issues/10#issuecomment-490634346)`
`113`	`114`
`114`	`115`	`## Using the CLI`
`115`	`116`