Vegvisir is a work in progress, based on a framework I developed for a company a few years ago, which in turn was based on a content injector I built for another company. You can read more about the history of this framework on my personal website.
Adding a Vegvisir version number after "/docs" in the pathname /docs/vX.X.X/example-docs-page lets you read the docs for a specific release.
This website (and the framework itself) is a work in progress. I apologize for the rushed, incomplete, confusing documentation on this site. I will make an effort to update these pages as best as I can.
The simple answer to what Vegvisir does is that it will automatically find and bind navigation handlers for all HTMLAnchorElements on a website. If the anchor href points to a page on the same origin; a PHP file (containing HTML and native PHP templating) from the website's public_path will be automatically soft-navigated to.
Another thing that Vegvisir lets you do with those soft-navigated pages is to inject and minify assets such as CSS stylesheets, JavaScript source files, and other assets that output text.
And the last thing that Vegvisir will offer for you is embeding snippets of PHP code (or another page) into a page.