Not able to install on M1

**Describe the bug**

I'm trying to install camelot v0.10.1 on my mac with M1 chip but I'm getting

```
ERROR: Could not find a version that satisfies the requirement pdftopng>=0.2.3; extra == "base" (from camelot-py[base]) (from versions: 0.1.0)
```

when trying to install with

```
pip install "camelot-py[base]==0.10.1"
```

The reason is `pdftopng` is not available for arm64.

I assume the best solution is a fix in `pdftopng` but maybe it shouldn't be a strict dependency? Currently downgrading to 0.9.0 works.

**Environment**

- OS: [e.g. macOS]: macOS
- Python version: 3.8
- Camelot version: 0.10.1

**Additional context**

Issue related in [`pdftopng`](https://github.com/vinayak-mehta/pdftopng/issues/8)

Start by reproducing the reported command, `pip install "camelot-py[base]==0.10.1"`, on an arm64 macOS environment and inspect how the `base` extra requires pdftopng. Review the related pdftopng issue before choosing an approach. Done means the installation behavior for supported M1 environments is resolved without breaking the base extra.

Written by the indexing model from the issue text.