docs(mdbook): Add title and gitlab links

This patch adds a title to the documentation as well as some links to
the repository as well as the WebIDE for GitLab adjustments.

docs/book.toml

 [book]
-authors = []
+title = "Shivering-Isles GitOps Infrastructure"
+authors = ["Sheogorath"]
 language = "en"
 multilingual = false
 src = "src"
+
+[output.html]
+git-repository-url = "https://git.shivering-isles.com/shivering-isles/infrastructure-gitops/-/tree/main/docs"
+edit-url-template = "https://git.shivering-isles.com/-/ide/project/shivering-isles/infrastructure-gitops/edit/main/-/docs/{path}"

docs/src/about.md

-# Shivering Isles GitOps Infrastructure
+# About
 
 This documentation provides some insight into the Sivering-Isles GitOps Infrastructure. Into concepts, useful information and a general overview over all the different parts of the overall project.