Add doc workflow

[ericpre]

Documentation for reusable workflow: https://docs.github.com/en/actions/using-workflows/reusing-workflows#calling-a-reusable-workflow

Progress of the PR

• [x] Add doc workflow using reusable workflow from hyperspy organisation (https://github.com/hyperspy/.github/blob/main/workflows/doc.yml),
• [x] fix external links
• [n/a] docstring updated (if appropriate),
• [x] update user guide (if appropriate),
• [n/a] added tests,
• [x] added line to CHANGES.rst,

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (f8745f9) 94.41% compared to head (8062ec4) 94.41%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #13 +/- ## ======================================= Coverage 94.41% 94.41% ======================================= Files 12 12 Lines 591 591 ======================================= Hits 558 558 Misses 33 33 ```

:umbrella: View full report in Codecov by Sentry.
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[ericpre]

looks good, but currently not running through

It pick up the mistake in the changelog! 😄

Warning: ../CHANGES.rst:2: WARNING: Duplicate explicit target name: "#11".
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
copying assets... copying static files... done
copying extra files... done
done
writing output... [  7%] api/data
writing output... [ 13%] api/index
writing output... [ 20%] api/reconstruct
writing output... [ 27%] api/signals
writing output... [ 33%] api/tools
writing output... [ 40%] changes
writing output... [ 47%] citing
writing output... [ [53](https://github.com/hyperspy/holospy/actions/runs/6824455928/job/18560396825?pr=13#step:9:54)%] contributing
writing output... [ [60](https://github.com/hyperspy/holospy/actions/runs/6824455928/job/18560396825?pr=13#step:9:61)%] index
writing output... [ [67](https://github.com/hyperspy/holospy/actions/runs/6824455928/job/18560396825?pr=13#step:9:68)%] license
writing output... [ [73](https://github.com/hyperspy/holospy/actions/runs/6824455928/job/18560396825?pr=13#step:9:74)%] user_guide/bibliography
writing output... [ [80](https://github.com/hyperspy/holospy/actions/runs/6824455928/job/18560396825?pr=13#step:9:81)%] user_guide/electron_holography
writing output... [ 87%] user_guide/index
writing output... [ 93%] user_guide/installation
writing output... [100%] user_guide/metadata_structure
generating indices... genindex py-modindex done
writing additional pages... search done
copying images... [ 50%] user_guide/images/holography_unwrapped_phase.png
copying images... [100%] user_guide/images/holography_argand_diagram.png
dumping search index in English (code: en)... done
dumping object inventory... done
build finished with problems, 1 warning.
make: *** [Makefile:20: html] Error 1