update all icon asset links to be absolute using site-urls plugin

docs/documentation/additional_software.md

docs/documentation/analysis/index.md

docs/documentation/libraries/index.md

docs/documentation/sizing/index.md

docs/get-involved/build-environment/windows.md

docs/get-involved/build/general.md

docs/get-involved/contribute.md

docs/get-involved/style/python-modularization.md

docs/partners.md

docs/tutorials/changing-design-specifications.md

docs/tutorials/standalone.md

docs/workflow.md

mkdocs.yml