[ANN] VSCode OCaml Platform v1.6.0

On behalf of the vscode-ocaml-platform team, I’m pleased to announce 1.6.0. This release contains a new activity tab for managing opam switches developed by @tmattio. We hope you find it useful.

Change log:

- Highlight token aliases in Menhir associativity declarations (#473)

- Activate the extension when workspace contains OCaml, Reason sources or
  project marker files. (#482)

- Add `ocaml.useOcamlEnv` setting to determine whether to use `ocaml-env` for
  opam commands from OCaml for Windows (#481)

- Fix terminal creation when using default shell and arguments (#484)

- Add an OCaml activity tab.

  The activity tab provides three views: the available switches, the build
  commands and an Help and Feedback section with links to community channels.

- Support `eliom` and `eliomi` file extensions (#487)

- Fix ocaml/ocaml-lsp#358: automatic insertion of an inferred interface was
  inserting code incorrectly on the second switch to the newly created (unsaved)
  `mli` file. If the new `mli` file isn't empty, we don't insert inferred
  interface (#498)