Mkdocs-risonia-theme

- [optional lazy loading of all images](https://github.com/unverbuggt/mkdocs-risonia-theme/commit/9b67690ea4bd9c07fc9b5cc03e0d3e43cc20e06e)
- [allow building of additional color themes (and use them to visualize decryption of encryptcontent plugin)](https://github.com/unverbuggt/mkdocs-risonia-theme/commit/e61972671428e2970967dbb6a20d4a71e46013e0)
- [fix don't send links to _blank if target specified](https://github.com/unverbuggt/mkdocs-risonia-theme/commit/f51e9d2ac01bb8659f39cec2a973fd304dd2e565)
- various other bugfixes

Bugfix of menu accordions
replace extra_javascript construct (hopefully understood MkDocs 1.5.0 announcement correctly)

Optionally make images zoomable on click (also add lazy loading)

relative font scaling

fix bug regarding "extblank" feature