docs: restructure docs (#14421)

Closes #13434 
Supersedes #14182

---------

Co-authored-by: Ethan <39577870+ethanndickson@users.noreply.github.com>
Co-authored-by: Ethan Dickson <ethan@coder.com>
Co-authored-by: Ben Potter <ben@coder.com>
Co-authored-by: Stephen Kirby <58410745+stirby@users.noreply.github.com>
Co-authored-by: Stephen Kirby <me@skirby.dev>
Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>
Co-authored-by: Edward Angert <EdwardAngert@users.noreply.github.com>

docs/user-guides/workspace-dotfiles.md

@@ -0,0 +1,71 @@
+# Dotfiles
+
+<!-- markdown-link-check-disable -->
+
+Coder offers the `coder dotfiles <repo>` command which simplifies workspace
+personalization. Our behavior is consistent with Codespaces, so
+[their documentation](https://docs.github.com/en/codespaces/customizing-your-codespace/personalizing-codespaces-for-your-account#dotfiles)
+explains how it loads your repo.
+
+<!-- markdown-link-check-enable -->
+
+You can read more on dotfiles best practices [here](https://dotfiles.github.io).
+
+## From templates
+
+Templates can prompt users for their dotfiles repo URL, which will personalize
+your workspace automatically.
+
+![Dotfiles in workspace creation](../images/user-guides/dotfiles-module.png)
+
+> Template admins: this can be enabled quite easily with a our
+> [dotfiles module](https://registry.coder.com/modules/dotfiles) using just a
+> few lines in the template.
+
+## Personalize script
+
+Templates may be configured to support executing a `~/personalize` script on
+startup which users can populate with commands to customize their workspaces.
+
+You can even fill `personalize` with `coder dotfiles <repo>`, but those looking
+for a simpler approach can inline commands like so:
+
+```bash
+#!/bin/bash
+sudo apt update
+# Install some of my favorite tools every time my workspace boots
+sudo apt install -y neovim fish cargo
+```
+
+> Template admins: refer to
+> [this module](https://registry.coder.com/modules/personalize) to enable the
+> `~/personalize` script on templates.
+
+## Setup script support
+
+User can setup their dotfiles by creating one of the following script files in
+their dotfiles repo:
+
+- `install.sh`
+- `install`
+- `bootstrap.sh`
+- `bootstrap`
+- `script/bootstrap`
+- `setup.sh`
+- `setup`
+- `script/setup`
+
+If any of the above files are found (in the specified order), Coder will try to
+execute the first match. After the first match is found, other files will be
+ignored.
+
+The setup script must be executable, otherwise the dotfiles setup will fail. If
+you encounter this issue, you can fix it by making the script executable using
+the following commands:
+
+```shell
+cd <path_to_dotfiles_repo>
+chmod +x <script_name>
+git commit -m "Make <script_name> executable" <script_name>
+git push
+```