feat: add docs website

docs/configuration/index.qmd

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+---
+title: Configuration
+---
+
+In R on Linux, packages are downloaded from CRAN as source packages.
+The default CRAN mirror is `https://cloud.r-project.org`.
+The default repository URL needs to be **actively changed** to one providing binaries for the respective Linux distribution.
+This can be done either for all users of the system, on a project level or for specific users only.
+All options will be shown in the following.
+
+## URL Scheme
+
+The URL scheme for this project is the same for all operating systems and only differs in the OS and architecture identifiers.
+
+::: {.callout-note icon=false}
+
+## URL scheme 
+
+`https://cran.devxy.io/<architecture>/<os>/latest`
+:::
+
+For example, the URL for Alpine Linux 3.21 for `arm64` would be `https://cran.devxy.io/arm64/alpine321/latest`.
+
+The architecture identifiers are:
+
+- `arm64`
+- `amd64`
+
+The OS identifiers are:
+
+- `jammy` (Ubuntu 22.04)
+- `noble` (Ubuntu 24.04)
+- `rhel8` (RedHat Enterprise Linux 8)
+- `rhel9` (RedHat Enterprise Linux 9)
+- `alpine320` (Alpine Linux 3.20)
+- `alpine321` (Alpine Linux 3.21)
+
+## Repository Configuration
+
+### System-wide
+
+To configure the default R repository for all users of a system, create/edit `$R_HOME/etc/Rprofile.site`.
+The location of this file depends on how R has been installed.
+To find its location, execute `R -q -e "paste0(Sys.getenv('R_HOME'),'/etc/Rprofile.site')"`.
+
+**At the bottom** of the file, add the following:
+
+```r
+options(repos = structure(c(CRAN = "<URL>")))
+```
+
+The name "CRAN" is optional.
+It is the canonical default and in some cases also used for special actions (e.g. in Posit Workbench and [{pak}](https://github.com/r-lib/pak)).
+Unless you have a good reason, it is advisable to stick with that name.
+
+### User-wide
+
+To change the default repository option for a specific *user*, add the line from above to `~/.Rprofile`.
+
+### Project-wide
+
+To change the default repository option for a specific *project*, add the line from above to `.Rprofile` in the project root directory in which R is started.
+
+## Verification
+
+When starting R, execute `getOption("repos")` to verify the repository is correctly configured.