run cargo diet to reduce crate size by 85%

I noticed the crate is pretty big and took a quick look, here
is the outcome of slimming it down.

```
➜  termscp git:(main) cargo diet
┌───────────────────────────────────────────┬─────────────┐
│ File                                      │ Size (Byte) │
├───────────────────────────────────────────┼─────────────┤
│ codecov.yml                               │          96 │
│ .github/ISSUE_TEMPLATE/feature_request.md │         203 │
│ dist/deb.sh                               │         210 │
│ .github/workflows/macos.yml               │         319 │
│ .github/workflows/windows.yml             │         321 │
│ dist/rpm.sh                               │         336 │
│ dist/build/README.md                      │         345 │
│ .gitignore                                │         356 │
│ dist/build/x86_64/Dockerfile              │         509 │
│ dist/pkgs/arch/.SRCINFO                   │         511 │
│ .github/workflows/aur-pub.yml             │         570 │
│ dist/pkgs/arch/PKGBUILD                   │         580 │
│ .github/ISSUE_TEMPLATE/bug_report.md      │         598 │
│ dist/build/x86_64_archlinux/Dockerfile    │         905 │
│ .github/workflows/linux.yml               │        1013 │
│ .github/PULL_REQUEST_TEMPLATE.md          │        1093 │
│ dist/build/deploy.sh                      │        1291 │
│ docs/drawio/UI.drawio                     │        1993 │
│ CODE_OF_CONDUCT.md                        │        3368 │
│ CONTRIBUTING.md                           │       10756 │
│ assets/images/bookmarks.gif               │      298453 │
│ assets/images/auth.gif                    │      321769 │
│ assets/images/explorer.gif                │      650583 │
│ assets/images/config.gif                  │      705780 │
│ assets/images/text-editor.gif             │     1898000 │
└───────────────────────────────────────────┴─────────────┘
Saved 85% or 3.9 MB in 25 files (of 4.6 MB and 75 files in entire crate)
```

Please let me know if you would like some other files to be included
or whatever else is needed to make this PR mergeable.

Thanks :).

Cargo.toml

@@ -11,6 +11,7 @@ homepage = "https://github.com/veeso/termscp"
 repository = "https://github.com/veeso/termscp"
 documentation = "https://docs.rs/termscp"
 readme = "README.md"
+include = ["src/**/*", "LICENSE", "README.md", "CHANGELOG.md"]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html