Document P6_DOC_TEST_FUDGE env var

Author: zoffixznet

README.md

@@ -163,6 +163,7 @@ explains briefly how to get started contributing documentation.
 
 - `P6_DOC_TEST_VERSBOSE` to a true value to display verbose messages during test suite run.
 Helpful when debugging failing test suite.
+- `P6_DOC_TEST_FUDGE` fudges `skip-test` code examples as TODO in `xt/examples-compilation.t` test
 
 # LICENSE