Support for a new file format

[Peter Dyballa]

Hello!

Rust, https://www.rust-lang.org, has additional files that have file names 
ending in .crate. The file command says they are GZipped. So I created a 
hard-link file.gz from a crate file and looked in GNU Emacs 27.2 into it. It 
looked like a TAR file, so a CRATE file must be a GZipped TAR file:

        pete 65 /\ tar -vtf yansi-term-0.1.2.crate
        -rw-r--r--  0 0      0          74 31 Mai  2020 
yansi-term-0.1.2/.cargo_vcs_info.json
        -rw-r--r--  0 1000   1000      860 31 Mai  2020 
yansi-term-0.1.2/.github/workflows/checks.yml
        -rw-r--r--  0 1000   1000     1629 31 Mai  2020 
yansi-term-0.1.2/.github/workflows/linux.yml
        -rw-r--r--  0 1000   1000     1469 31 Mai  2020 
yansi-term-0.1.2/.github/workflows/osx.yml
        -rw-r--r--  0 1000   1000       25 31 Mai  2020 
yansi-term-0.1.2/.gitignore
        -rw-r--r--  0 1000   1000      529 31 Mai  2020 
yansi-term-0.1.2/.travis.yml
        -rw-r--r--  0 0      0        4415 31 Mai  2020 
yansi-term-0.1.2/Cargo.lock
        -rw-r--r--  0 0      0        1549 31 Mai  2020 
yansi-term-0.1.2/Cargo.toml
        -rw-r--r--  0 1000   1000      983 31 Mai  2020 
yansi-term-0.1.2/Cargo.toml.orig
        -rw-r--r--  0 1000   1000     1080 31 Mai  2020 yansi-term-0.1.2/LICENCE
        -rw-r--r--  0 1000   1000     4203 31 Mai  2020 
yansi-term-0.1.2/README.md
        -rw-r--r--  0 1000   1000     1626 31 Mai  2020 
yansi-term-0.1.2/examples/256_colours.rs
        -rw-r--r--  0 1000   1000      816 31 Mai  2020 
yansi-term-0.1.2/examples/basic_colours.rs
        -rw-r--r--  0 1000   1000      425 31 Mai  2020 
yansi-term-0.1.2/examples/overwrite.rs
        -rw-r--r--  0 1000   1000      592 31 Mai  2020 
yansi-term-0.1.2/examples/rgb_colours.rs
        -rw-r--r--  0 1000   1000    12938 31 Mai  2020 
yansi-term-0.1.2/src/ansi.rs
        -rw-r--r--  0 1000   1000     2103 31 Mai  2020 
yansi-term-0.1.2/src/display.rs
        -rw-r--r--  0 1000   1000     5999 31 Mai  2020 
yansi-term-0.1.2/src/lib.rs
        -rw-r--r--  0 1000   1000    14209 31 Mai  2020 
yansi-term-0.1.2/src/style.rs
        -rw-r--r--  0 1000   1000     2375 31 Mai  2020 
yansi-term-0.1.2/src/windows.rs

Could next version of GNU Emacs support this for 
dired-mode/jka-compression-mode?

--
Greetings

  Pete

It is so hot in some places that the people there have to live in other places.