docs: add --assets usage documentation

docs/developer-guide/cli-methods/bundle-the-basemaps-assets-archive.md

@@ -55,6 +55,80 @@ Clone the [**linz/basemaps-config**][bm_config_repo] repository to your machine.
         ```bash
         $BM_SPRITES_BIN = $BM_REPO/packages/sprites/bin
         ```
+
+## Generate the `basemaps` assets
+
+### 1. Create local directory
+
+To prepare for bundling the `basemaps` assets archive, create a local directory on your machine with the following subdirectory structure:
+
+```md
+- assets
+  - fonts
+  - sprites
+```
+
+You can specify a location and directory name of your choice.
+
+!!! abstract "Path"
+
+    On your machine, consider the following path:
+
+    === "`ASSETS_DIR`"
+
+        The path to the created directory on your machine.
+
+        ```bash
+        $ASSETS_DIR = {path_to_directory}
+        ```
+
+### 2. Convert fonts into `.pbf` (protobuf-encoded glyphs) files
+
+To generate the `basemaps` `.pbf` files, follow the instructions described in this [README.md][fonts_readme] file. Alternatively, there is a [repository][pbf_fonts_repo] containing various fonts that have already been converted into the `.pbf` format.
+
+Move the generated and/or downloaded collections of `.pbf` files **into** the following directory:
+
+```
+$ASSETS_DIR/assets/fonts
+```
+
+The contents of your `$ASSETS_DIR/assets/fonts` directory should look similar to the following:
+
+```md
+- $ASSETS_DIR/assets/fonts
+  - Noto Sans Bold
+    - 0-255.pbf
+    - ...
+  - Open Sans Bold
+    - 0-255.pbf
+    - ...
+```
+
+### 3. Convert sprite files into sprite sheets
+
+Use the following command to generate the `basemaps` sprite sheets from the collection of topographic sprite files:
+
+```bash
+node $BM_SPRITES_BIN/basemaps-sprites.mjs \
+$BM_CONFIG_REPO/config/sprites/topographic
+```
+
+The above command will output the resulting sprite sheets to the location from which you executed the command. Move the outputted files **into** the following directory:
+
+```md
+$ASSETS_DIR/assets/sprites
+```
+
+The contents of your `$ASSETS_DIR/assets/sprites` directory should look similar to the following:
+
+```md
+- $ASSETS_DIR/assets/sprites
+  - topographic.json
+  - topographic.png
+  - [email protected]
+  - [email protected]
+```
+
 ## Run the `basemaps/cli` package
 
 ### Command
@@ -63,15 +137,15 @@ Use the following command to bundle the `basemaps` assets archive:
 
 ```bash
 node $BM_CLI_BUILD/bin.js bundle-assets \
-    --assets $BM_CONFIG_REPO/assets \
+    --assets $ASSETS_DIR \
     --output assets.bundle.tar.co \
 ```
 
 ### Parameters
 
 === "`--assets`"
 
-    Specifies the location of the assets folder to use. This folder refers to that of which is within the `basemaps-config` repository.
+    Specifies the location of the assets folder to use. This folder refers to that which contains the `.pbf` files and sprite sheets on your local machine.
 
 === "`--output`"
 
@@ -80,3 +154,5 @@ node $BM_CLI_BUILD/bin.js bundle-assets \
 <!-- external links -->
 
 [bm_config_repo]: https://github.com/linz/basemaps-config
+[fonts_readme]: https://github.com/linz/basemaps-config/tree/master/config/fonts
+[pbf_fonts_repo]: https://github.com/korywka/fonts.pbf