`getNearestCommand` makes bold assumptions about the user input

[carafelix]

The line responsible for selecting the text to be search against while looking for similar command names makes too much assumptions about the user input and dev preferences regarding what is a command and where it's located https://github.com/grammyjs/commands/blob/9303b26c4b793c1ff0a9b09feb3b4ef931fc5c86/src/context.ts#L74 implies that:

• the prefix is always 1 character long.
• the command is always at the start.
• the user input only contains a command, and nothing else.

this assumptions are contradictory with the plugin features that:

• allow for arbitrary length custom prefixes
• allow for matching commands at any position

and contradictory with the user unexpected behavior of typing:

• '/myCommand and some text'

this could be mitigated making use of the proposed addition of hydrated command entities in #31