docs(no-get-by-for-checking-element-not-present): fix rule reference in README (#74)

Missing .md extension

Author: arvigeus

README.md

@@ -141,7 +141,7 @@ To enable this configuration use the `extends` property in your
 | [no-await-sync-query](docs/rules/no-await-sync-query.md)                                            | Disallow unnecessary `await` for sync queries                               | ![recommended-badge][] ![angular-badge][] ![react-badge][] ![vue-badge][] |                    |
 | [no-debug](docs/rules/no-debug.md)                                                                  | Disallow the use of `debug`                                                 | ![angular-badge][] ![react-badge][] ![vue-badge][]                        |                    |
 | [no-dom-import](docs/rules/no-dom-import.md)                                                        | Disallow importing from DOM Testing Library                                 | ![angular-badge][] ![react-badge][] ![vue-badge][]                        | ![fixable-badge][] |
-| [no-get-by-for-checking-element-not-present](docs/rules/no-get-by-for-checking-element-not-present) | Disallow the use of `getBy*` queries when checking elements are not present |                                                                           |                    |
+| [no-get-by-for-checking-element-not-present](docs/rules/no-get-by-for-checking-element-not-present.md) | Disallow the use of `getBy*` queries when checking elements are not present |                                                                           |                    |
 | [no-manual-cleanup](docs/rules/no-manual-cleanup.md)                                                | Disallow the use of `cleanup`                                               |                                                                           |                    |
 | [prefer-explicit-assert](docs/rules/prefer-explicit-assert.md)                                      | Suggest using explicit assertions rather than just `getBy*` queries         |                                                                           |                    |