Upload nightly wheels for PyWavelets to the Scientific Python Nightly Wheels index on Anaconda

[agriyakhetarpal]

Description

This PR updates the emscripten.yml workflow to establish uploads of nightly WASM wheels on an Anaconda-hosted PyPI index at https://anaconda.org/scientific-python-nightly-wheels/pywavelets.

With the configuration set here, this shall overwrite existing wheels if present.

Proposed changes

The changes here are as follows:

1. A schedule to upload wheels
2. A workflow_dispatch event to trigger manual uploads if needed
3. A step with conditions set so that the cadence of the wheel upload adheres to a push to master, a manually-triggered workflow, and on this repository only – not on forks

Footnotes

Please see #706 for more information.

This closes scientific-python/upload-nightly-action#75.

[rgommers]

This seems straightforward enough, thanks @agriyakhetarpal. I guess we'll only know if it works once we merge and try an upload, so let's do that proactively - I only have a minor comment so far.

[rgommers]

Thanks! Let's give this a go now

[agriyakhetarpal]

It worked, we have the wheel at https://anaconda.org/scientific-python-nightly-wheels/PyWavelets/files

[rgommers]

Great! Everything in the CI log looks as expected too, so we're all set here.