Update arguments of API for linters in README.md (#535)

README.md

@@ -216,10 +216,11 @@ Instead of declaring the linter as a table, you can also declare it as a
 function which returns the linter table in case you want to dynamically
 generate some of the properties.
 
-`your_parse_function` can be a function which takes two arguments:
+`your_parse_function` can be a function which takes three arguments:
 
 - `output`
 - `bufnr`
+- `linter_cwd`
 
 
 The `output` is the output generated by the linter command.
@@ -246,7 +247,7 @@ using the function in the `lint.parser` module:
 parser = require('lint.parser').from_errorformat(errorformat)
 ```
 
-The function takes a single argument which is the `errorformat`.
+The function takes two arguments: `errorformat` and `skeleton` (optional).
 
 
 ### from_pattern