fix: #23 #28 #35 list with map of lists issue

[carlmontanari]

👋 I ran into the same issue as in #23 #28 and #35 today. it looks like #28 hasn't been updated so took the tweaks that they had made and put them here. I made a bit more elaborate of a test based on the exact issue I encountered. with the changes in my local vendored copy things are working as expected!

I also changed the test here to expect failure as I dont think that is valid?

  - a
- b

at least the above complains in yaml validators and such and with the tweaks in this pr it raises the expected UnexpectedToken error.

unrelated, but I also think that with the recent changes the test package may need to get included in build.zig.zon since the build file imports from there -- works fine for local/vendored but not when including in my build.zig.zon as dep. happy to make another quick patch for this or can include here if wanted. looks like sorted by #51 :)

im super new to zig so hopefully this is all cool. thanks for making this package! 🥳

edit to include before/after output:

before:

modes:
    - name: a
      fooers:
          - name: b
            do_thing:
                thing: blah
          - name: b
            fooers:
                - name: a
                  do_thing:
                      input: blah
                - name: c
                  do_thing:
                      input: blah
                - name: d
                  do_thing:
                      input: blah
                - name: c
                  fooers:
                      - name: b
                        do_thing:
                            input: blah
                      - name: d
                        fooers:
                            - name: b
                              do_thing:
                                  input: blah

and after:

modes:
    - name: a
      accessible_modes:
          - name: b
            do_thing:
                thing: blah
    - name: b
      accessible_modes:
          - name: a
            do_thing:
                thing: blah
          - name: c
            do_thing:
                thing: blah
          - name: d
            do_thing:
                thing: blah
    - name: c
      accessible_modes:
          - name: b
            do_thing:
                thing: blah
    - name: d
      accessible_modes:
          - name: b
            do_thing:
                thing: blah

[kubkon]

Looks good, thanks!