Markdown-spa

- Using UTF-8 encoding for all `open` calls

Converting meta values to int if necessary
➔ Fixes `order` sorted alphabetically instead of numerically

Updated github actions that use node 16:
- `actions/setup-python4.7.1` → `actions/setup-pythonv5`
- `actions/configure-pagesv3` →`actions/configure-pagesv4`
- `actions/upload-pages-artifactv2` → `actions/upload-pages-artifactv3`
- `actions/deploy-pagesv2` → `actions/deploy-pagesv4`

- Fixed weird behavior when popstate is triggered
- Accounting for nested elements when clicking on a link
- Reduced amount of updates while page transitions

Fixed update function not called when `<a>` is the parent of the event's target.

Updating pages now uses specific functions, see [documentation](https://mrspaar.github.io/markdown_spa/features/spa/) for full details.