feat: add ability to extend hermione.ctx typings

[KuznetsovRoman]

Resolves #883

Usage example

• Extend interface HermioneCtx from module "hermione":

  
  // global.d.ts
  import type { HermioneCtx } from "hermione";

declare module "hermione" { interface HermioneCtx { someVariable: string; } }

- Use `hermione.ctx` with extended typings:
```ts
hermione.ctx.someVariable // string