Suggestion: add a flag in the config.yaml to change the prefix(!)

[Damaj301damaj-lol]

Allow modification of the prefix of the commands, it is a trivial thing to do as in, you probably only need to modify these files to replace !discord and !matrix with a var that can be set in the config.yaml:

discordcommandhandler.ts
matrixcommandhandler.ts
provisioner.ts

which isn't much, only 1/2 lines, but i suck at TS, so i cannot do a PR