Fix broken links in PyPI README

[maresb]

I noticed that the images on PyPI are broken, so this is basically just a copy-paste from pymc-labs/pymc-marketing#1051.

Use the hatch-fancy-pypi-readme plugin to fix broken links on PyPI.

To view differences, run

pipx run hatch-fancy-pypi-readme > pypi-readme.md
diff README.md pypi-readme.md

Result:

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<   <img src="labelle.png" alt="logo" width="400"></img>
---
>   <img src="https://raw.githubusercontent.com/labelle-org/labelle/main/labelle.png" alt="logo" width="400"></img>
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< Labelle is not affiliated with DYMO. Please see the [disclaimer](#disclaimers) below.
---
> Labelle is not affiliated with DYMO. Please see the [disclaimer](https://github.com/labelle-org/labelle/tree/main/#disclaimers) below.
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< [adding the device id](src/labelle/lib/constants.py). Once you can print,
---
> [adding the device id](https://github.com/labelle-org/labelle/tree/main/src/labelle/lib/constants.py). Once you can print,
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< by following [these instructions](doc/margin-calibration-howto.md).
---
> by following [these instructions](https://github.com/labelle-org/labelle/tree/main/doc/margin-calibration-howto.md).
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< Default fonts are managed via [labelle.ini](labelle.ini).
---
> Default fonts are managed via [labelle.ini](https://github.com/labelle-org/labelle/tree/main/labelle.ini).
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< See [here](vendoring/README.md) for more information and
< [LICENSE](src/labelle/_vendor/matplotlib/LICENSE) for the license.
---
> See [here](https://github.com/labelle-org/labelle/tree/main/vendoring/README.md) for more information and
> [LICENSE](https://github.com/labelle-org/labelle/tree/main/src/labelle/_vendor/matplotlib/LICENSE) for the license.
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< [SIL Open Font License](src/labelle/resources/fonts/LICENSE).
---
> [SIL Open Font License](https://github.com/labelle-org/labelle/tree/main/src/labelle/resources/fonts/LICENSE).
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< ![Batch mode example](doc/batch-example.png)
---
> ![Batch mode example](https://raw.githubusercontent.com/labelle-org/labelle/main/doc/batch-example.png)
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< ![alt](doc/Labelle_example_1.png)
---
> ![alt](https://raw.githubusercontent.com/labelle-org/labelle/main/doc/Labelle_example_1.png)
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< ![alt](doc/Labelle_example_2.png)
---
> ![alt](https://raw.githubusercontent.com/labelle-org/labelle/main/doc/Labelle_example_2.png)
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< ![alt](doc/Labelle_example_3.png)
---
> ![alt](https://raw.githubusercontent.com/labelle-org/labelle/main/doc/Labelle_example_3.png)
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< * This software is provided as-is, without any warranty. Please see [LICENSE](LICENSE)
---
> * This software is provided as-is, without any warranty. Please see [LICENSE](https://github.com/labelle-org/labelle/tree/main/LICENSE)
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>