Styling updates + wiki page on contributions and sankey

[marc-vdm]

@mrvisscher Please:

• Update contribution analysis figure for windows
• Update Sankey figure
  • Install DB below, run calculation with 1 steel and IPCC 2021
  • Screenshot result (or save as .svg and edit to reasonable size
• Store screenshots in docs/wiki/assets, overwrite current files.

wiki_ca_example.xlsx

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation
  • For in-code documentation, please follow the numpy style guide.
  • For user documentation, please update the wiki in
    ./activity_browser/docs/wiki
• Update tests.
• Link this PR to related issues by using closing keywords.

If you have write access (otherwise a maintainer will do this for you):

• Categorize the PR by setting a good title and adding one of the labels:
  bug, feature, ui, change, documentation, breaking, ci
  as they show up in the changelog.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.

[coveralls]

coverage: 54.26% (+0.03%) from 54.228%
when pulling 903add2 on marc-vdm:lca_results_wiki
into 9d4a1c4 on LCA-ActivityBrowser:main.

[mrvisscher]

LGTM