Transform repo into a workspace

[dodomorandi]

This is the first step toward implementing different layers of implementation.

There are many things that need to be addressed before merge:

• [x] Update README.md
• [x] Fix/Improve release action for Dgc
• [x] Update RELEASE.md

Let me know what do you think. If you want, I can move the branch from my repo to rust-italia, in order to let you directly commit changes.

[codecov-commenter]

Codecov Report

Merging #41 (987a745) into main (926a814) will decrease coverage by 0.26%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   85.00%   84.73%   -0.27%     
==========================================
  Files          10       11       +1     
  Lines        1040      989      -51     
==========================================
- Hits          884      838      -46     
+ Misses        156      151       -5     

Impacted Files	Coverage Δ
dgc/src/cwt.rs	80.00% <ø> (ø)
dgc/src/dgc.rs	93.84% <ø> (ø)
dgc/src/dgc_container.rs	78.00% <ø> (ø)
dgc/src/lib.rs	100.00% <ø> (ø)
dgc/src/parse.rs	73.28% <ø> (ø)
dgc/src/recovery.rs	50.00% <ø> (ø)
dgc/src/test.rs	96.00% <ø> (ø)
dgc/src/trustlist.rs	58.33% <ø> (ø)
dgc/src/vaccination.rs	50.00% <ø> (ø)
dgc/src/valuesets.rs	100.00% <ø> (ø)
... and 2 more

---

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[dodomorandi]

I think that things should be sufficient for now, what do you think? I decided to use simlinks for dgc/README.md and the LICENSE file, just like have been done in serde.

Let me know if you are satisfied with the current stub of the READMEs, we can improve them later (and we will :grin:).

[lmammino]

Awesome work @dodomorandi . Just left some small comments around the GitHub actions. These are not blockers though, we could always revisit these later

[lmammino]

let's 🚢 !

:shipit: