docs: add Cancel Nil virus to readme list of viruses

readme.md

@@ -122,6 +122,7 @@ The table below presents all available options.
 | [`arithmeticassignment`](viruses/arithmeticassignment/arithmeticassignment.go)                   | Arithmetic Assignment        | Replaces `+=`, `-=`, `*=`, `/=`, `%=`, `&=`, <code>&#124;=</code>, `^=`, `<<=`, `>>=` and `&^=` with `=`.                                                                                                                       |
 | [`arithmeticassignmentinvert`](viruses/arithmeticassignmentinvert/arithmeticassignmentinvert.go) | Arithmetic Assignment Invert | Replaces `+=` with `-=`, `*=` with `/=`, `%=` with `*=` and vice versa.                                                                                                                                                         |
 | [`bitwise`](viruses/bitwise/bitwise.go)                                                          | Bitwise                      | Replaces `&` with <code>&#124;</code>, <code>&#124;</code> with `&`, `^` with `&`, `&^` with `&`, `<<` with `>>` and `>>` with `<<`.                                                                                            |
+| [`cancelnil`](viruses/cancelnil/cancelnil.go)                                                    | Cancel Nil                   | Changes calls to [`context.CancelCauseFunc`](https://pkg.go.dev/context#CancelCauseFunc) to pass nil.                                                                                                                           |
 | [`comparison`](viruses/comparison/comparison.go)                                                 | Comparison                   | Replaces `<` with `<=`, `>` with `>=` and vice versa.                                                                                                                                                                           |
 | [`comparisoninvert`](viruses/comparisoninvert/comparisoninvert.go)                               | Comparison Invert            | Replaces `>` with `<=`, `<` with `>=`, `==` with `!=` and vice versa.                                                                                                                                                           |
 | [`comparisonreplace`](viruses/comparisonreplace/comparisonreplace.go)                            | Comparison Replace           | Replaces the left and right sides of an `&&` comparison with `true` and the left and right sides of an <code>&#124;&#124;</code> with false. E.g. `1 == 1 && 2 == 2` gets two mutations: `true && 2 == 2` and `1 == 1 && true`. |