docs/configuring: add modules section

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I6a6a6964f2e65a11acab2a2f7413a5f94bff3815

docs/manual/configuring/modules.md

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+## Using the Module Interface {#ch-module-interface}
+
+Before describing the module interface, it is worth nothing that NVF is a hybrid
+wrapper. It does not lock you into one of Lua or Nix, and both languages are
+considered first-class citizens for configuring your editor. However, Nix is the
+primarily supported language for NVF. While [DAGs](#ch-using-dags) allow for the
+surgical insertion of Lua code into your configuration, in most cases you will
+be more interested in using or extending the Nix-based module system.
+
+### {#ch-using-modules}
+
+Up until v0.6, most modules exposed all supported plugin options as individual
+module options. With the release of v0.6, almost every module has been converted
+to a new `setupOpts` format that provides complete user freedom over a plugin's
+`setup({})` function.
+
+The anatomy of a typical **plugin** module consists of two primary options:
+
+`vim.<category>.<plugin>.enable` and `vim.<category>.<plugin>.setupOpts`. The
+first option is disabled by default, and dictates whether the plugin is enabled.
+If set to `true`, the plugin will be enabled and added to your Neovim's runtime
+path. The second is an attribute set (`{}`) that will be converted to the
+plugin's setup table. From Lua-based setups you may be used to something like
+this:
+
+```lua
+require("nvim-autopairs").setup({
+  check_ts = true,
+  disable_filetype = { "TelescopePrompt", "vim" }
+})
+```
+
+This is the typical setup table. It is sometimes expressed slightly differently
+(e.g., the table might be stored as a variable) but the gist is that you pass a
+table to the `setup()` function. The principle of `setupOpts` is the same. It
+converts a Nix attribute set to a Lua table using the `toLuaObject` function
+located in nvf's extended library. The same configuration would be expressed in
+Nix as follows:
+
+```nix
+{
+  setupOpts = {
+    check_ts = true; # boolean
+    disable_filetype = ["TelescopePrompt" "vim"]; # Lua table
+  };
+}
+```
+
+<!-- markdownlint-disable MD051 MD059 -->
+
+The `setupOpts` option is freeform, so anything you put in it will be converted
+to its Lua equivalent and will appear in your built `init.lua`. You can find
+details about `toLuaObject` [here](#sec-details-of-toluaobject). The top-level
+DAG entries in **nvf** are documented in the [DAG entries](#ch-dag-entries)
+section. You can read more about DAGs in the [using DAGs](#ch-using-dags)
+section.
+
+<!-- markdownlint-enable MD051 MD059 -->