Add linter rule for detecting regex-like network rule patterns

There are cases where a network rule pattern looks like a regular expression even though it is probably not.
For example:

```adblock
/foo/
```

It starts and ends with a slash but does not contain any [regexp syntax characters](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Literal_character#description).

In such cases, we can _suggest_ adding a trailing wildcard so that the pattern is not interpreted as a regular expression, making the network rule more optimal:

```adblock
/foo/*
```

Also, we may need to handle such cases as well:

```adblock
/foo/bar/
```