Unknown argument error when executing CLI with pages glob

## Environment

- MacOS 10.15.7
- zsh shell
- Node.js 12.18.4
- yarn 1.22.5

## Description

When I worked on [this PR](https://github.com/callstack/linaria/pull/320), and upgraded component-docs to then-latest version 0.23.0, I notice that the npm script `component-docs serve "docs/*.{md,mdx}"` now return this error:

```
$ component-docs serve "docs/*.{md,mdx}"
...
Unknown argument: docs/*.{md,mdx}
```

Event after recent update to 0.24.0, the issue still persists, so I have to resort to component-docs.config.js to define the pages collection.

If pages glob argument is no longer supported in recent update, I think it should be reflected in README to avoid confusion.

## Reproducible Demo

Just run below command and observe the error:

```
npx component-docs serve "example/**/*.md"
```