💥 Remove :feature category

:feature was a "catch-all" category. Many of its modules fit better in
other categories, so they've been moved:

- feature/debugger -> tools/debugger
- feature/evil -> editor/evil
- feature/eval -> tools/eval
- feature/lookup -> tools/lookup
- feature/snippets -> editor/snippets
- feature/file-templates -> editor/file-templates
- feature/workspaces -> ui/workspaces

More potential changes in the future:

- A new :term category for terminal emulation modules (eshell, term and
  vterm).
- A new :os category for modules dedicated to os-specific functionality.
  The :tools macos module would fit here, but so would modules for nixos
  and arch.
- A new :services category for web-service integration, like wakatime,
  twitter, elfeed, gist and pastebin services.

modules/editor/file-templates/templates/rust-mode/__Cargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "${1:Project Name}"
+version = "0.0.1"
+authors = [ "`user-full-name` <`user-mail-address`>" ]
+$0

modules/editor/file-templates/templates/rust-mode/__main.rs

@@ -0,0 +1,5 @@
+use std::io;
+
+fn main() {
+    ${0:println!("Hello, world!");}
+}