Compilation fails with latest Typescript

[pacien]

The compilation of matrix-appservice-discord fails with the latest version of the Typescript compiler (3.5.1).

The issue is partly due to an outdated dependency that needs to be updated: sindresorhus/p-queue#66.

src/bot.ts and src/store.ts also need to be adapted.

Compilation log:

> matrix-appservice-discord@0.5.0 build /nix/store/5xwznxq75pba6p0id9ip5qy0aixjzqdl-node_matrix-appservice-discord-0.5.0/lib/node_modules/matrix-appservice-discord
> tsc

node_modules/p-queue/index.d.ts(81,54): error TS2344: Type 'DefaultAddOptions' does not satisfy the constraint 'QueueAddOptions'.
  Index signature is missing in type 'DefaultAddOptions'.
src/bot.ts(156,50): error TS2345: Argument of type 'Promise<unknown>' is not assignable to parameter of type 'Promise<{}>'.
  Type 'unknown' is not assignable to type '{}'.
src/store.ts(69,9): error TS2322: Type 'unknown' is not assignable to type 'void | {}'.
  Type 'unknown' is not assignable to type '{}'.
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! matrix-appservice-discord@0.5.0 build: `tsc`
npm ERR! Exit status 2

[pacien]

Fixed by #489.