Provide /cmd help with list of possible commands and aliases

[mordamax]

• implement the way to define aliases for long commands

As I see from comments: most common expectation of simplicity is bot {command}. but this pattern is used in processbot, so we can't re-use here it probably

• send either link to help with list of commands & aliases or comment in PR

One of the options is - each pull-request (where bot is supported), the first comment would be listing all possible commands, or linking to docs with up-to-date list of supported bots and their commands (like tip bot, processbot, command bot, etc)

[shawntabrizi]

Ideally, there would be a list of "shortcut" commands which would map to the appropriate /cmd thing.

For example, benchmarking is quite a popular command, i would want a shortcut /benchmark which would be a string replace for /cmd queue -v RUST_LOG=debug -c bench-bot $.

All aliases could be listed in some JSON or similar.

Then I could write /benchmark runtime westend-dev pallet_balances rather than /cmd queue -v RUST_LOG=debug -c bench-bot $ runtime westend-dev pallet_balances

Its a small thing, but improves user experience quite a bit for me.