docs: added page describing cli tool

docs/cli.md

@@ -0,0 +1,153 @@
+Showdown comes bundled with a Command-line interface (CLI) tool that allows you to run Showdown converter from the command line.
+
+## Requirements
+
+* [Node.js](https://nodejs.org/en/)
+
+## Quick start guide
+
+1. Check that Showdown CLI is accessible.
+
+    * If you installed Showdown globally via `npm install showdown -g`, you can access the CLI tool help by typing `showdown -h` in the command line:
+
+        === "input"
+
+            ```sh
+            showdown -h
+            ```
+
+        === "output"
+
+            ```
+            Usage: showdown <command> [options]
+
+            CLI to Showdownjs markdown parser v3.0.0-alpha
+
+            Options:
+              -V, --version       output the version number
+              -q, --quiet         Quiet mode. Only print errors
+              -m, --mute          Mute mode. Does not print anything
+              -h, --help          display help for command
+
+            Commands:
+              makehtml [options]  Converts markdown into html
+              help [command]      display help for command
+            ```
+
+    * If you installed Showdown locally via `npm install showdown`, open the folder where Showdown is installed, and type `node ./bin/showdown.js -h` in the command line:
+
+        === "input"
+
+            ```sh
+            node ./bin/showdown.js -h
+            ```
+
+        === "output"
+
+            ```
+            Usage: showdown <command> [options]
+
+            CLI to Showdownjs markdown parser v3.0.0-alpha
+
+            Options:
+              -V, --version       output the version number
+              -q, --quiet         Quiet mode. Only print errors
+              -m, --mute          Mute mode. Does not print anything
+              -h, --help          display help for command
+
+            Commands:
+              makehtml [options]  Converts markdown into html
+              help [command]      display help for command
+            ```
+
+1. Use `makehtml` command to convert your document to HTML. For example:
+
+    !!! example "Convert `foo.md` into `bar.html`"
+        
+        ```sh
+        showdown makehtml -i foo.md -o bar.html
+        ```
+
+## Commands
+
+### `makehtml`
+
+Convert a Markdown input into HTML.
+
+**Usage**
+
+```sh
+showdown makehtml [options]
+```
+
+#### Options
+
+###### `-i / --input`
+
+* Short format: `-i`
+* Alias: `--input`
+* Description: Input source. Usually a `.md` file. If omitted or empty, reads from `stdin`.
+* Examples:
+
+    !!! example ""
+
+        ```sh
+        // Read from stdin and output to stdout
+        showdown makehtml -i
+
+        // Read from the foo.md file and output to stdout
+        showdown makehtml --input foo.md
+        ```
+
+###### `-o/--output`
+
+* Short format: `-o`
+* Alias: `--output`
+* Description: Output target. Usually a `.html` file. If omitted or empty, writes to `stdout`.
+* Example:
+
+    !!! example ""
+
+        ```sh
+        // Read from the foo.md file and output to bar.html
+        showdown makehtml -i foo.md -o bar.html
+        ```
+
+###### `-a/--append`
+
+* Short format: `-a`
+* Alias: `--append`
+* Description: Append data to output instead of overwriting.
+* Example: 
+
+    !!! example ""
+
+        ```sh
+        showdown makehtml -a
+        ```
+
+###### `-u/--encoding`
+
+* Short format: `-u`
+* Alias: `--encoding`
+* Description: Specify the input encoding.
+* Example: 
+    
+    !!! example ""
+
+        ```sh
+        showdown makehtml -u UTF8
+        ```
+
+###### `-e/--extensions`
+
+* Short format: `-e`
+* Alias: `--extension`
+* Description: Load the specified extension(s). Should be valid path(s) to Node-compatible extensions.
+* Example:
+
+    !!! example ""
+
+        ```sh
+        showdown makehtml -e ~/twitter.js -e ~/youtube.js
+        ```

mkdocs.yml

@@ -37,3 +37,4 @@ nav:
     - Showdown options: configuration.md
     - Available options: available-options.md
     - Flavors: flavors.md
+  - CLI: cli.md