Add docs for command filter

docs/dispatcher/filters/command.md

@@ -0,0 +1,32 @@
+# Command
+
+This filter can be helpful for handling commands from the text messages.
+
+Works only with [Message](../../api/types/message.md) events which have the `text`.
+
+## Specification
+| Argument | Type | Description |
+| --- | --- | --- |
+| `commands` |  `#!python3 List[CommandPatterType]` | List of commands (string or compiled regexp patterns) |
+| `commands_prefix` |  `#!python3 str` | Prefix for command. Prefix is always is single char but here you can pass all of allowed prefixes, for example: `"/!"` will work with commands prefixed by  `"/"` or `"!"` (Default: `"/"`). |
+| `commands_ignore_case` |  `#!python3 bool` | Ignore case (Does not work with regexp, use flags instead. Default: `False`) |
+| `commands_ignore_mention` |  `#!python3 bool` | Ignore bot mention. By default bot can not handle commands intended for other bots (Default: `False`) |
+
+
+## Usage
+
+1. Filter single variant of commands: `#!python3 Command(commands=["start"])`
+1. Handle command by regexp pattern: `#!python3 Command(commands=[re.compile(r"item_(\d+)")])`
+1. Match command by multiple variants: `#!python3 Command(commands=["item", re.compile(r"item_(\d+)")])`
+1. Handle commands in public chats intended for other bots: `#!python3 Command(commands=["command"], commands)`
+1. As keyword argument in registerer: `#!python3 @router.message_handler(commands=["help"])`
+
+!!! warning 
+    Command cannot include spaces or any whitespace
+
+## Allowed handlers
+
+Allowed update types for this filter:
+
+- `message`
+- `edited_message`

docs/dispatcher/filters/index.md

@@ -12,6 +12,7 @@ Here is list of builtin filters and event types where it can be used:
 | Filter                      | update | message | edited_message | channel_post | edited_channel_post | inline_query | chosen_inline_result | callback_query | shipping_query | pre_checkout_query | poll |
 | --------------------------- |:------:|:-------:|:--------------:|:------------:|:-------------------:|:------------:|:--------------------:|:--------------:|:--------------:|:------------------:|:----:|
 | [Text](text.md)             |        | +       | +              | +            | +                   | +            |                      | +              |                |                    | +    |
+| [Command](command.md)       |        | +       |                |              |                     |              |                      |                |                |                    |      |
 |                             |        |         |                |              |                     |              |                      |                |                |                    |      |