Incorrectly flattens arrays-of-arrays in freeform fields

[eropple]

Hey there! Been noodling with openapi-merger, it's a real help. Ran into a bug, though. If you have an example field (which is, by spec, freeform and should generally just be ignored), the merge logic in the library recurses down into it and seems to flatten arrays-of-arrays.

Example from a source file:

          content:
            application/json:
              schema:
                "$ref": "#/components/schemas/GetMetricTimeseriesDataResponse"
              example:
                total_row_count: 2
                timeframe:
                  - 1610029711
                  - 1610116111
                meta:
                  aggregation: "view_end"
                data:
                  - - '2021-01-07T14:00:00Z'
                    - '0.8743536882994202'
                    - '154240'
                  - - '2021-01-07T15:00:00Z'
                    - '0.8929105055911401'
                    - '156056'

And the result from a build that incorporates this file:

      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/GetMetricTimeseriesDataResponse'
              example:
                total_row_count: 2
                timeframe:
                  - 1610029711
                  - 1610116111
                meta:
                  aggregation: view_end
                data:
                  - '2021-01-07T14:00:00Z'
                  - '0.8743536882994202'
                  - '154240'
                  - '2021-01-07T15:00:00Z'
                  - '0.8929105055911401'
                  - '156056'

My temporary solution is in this branch and it unblocks my problem, but I'm sure it's not a complete solution.

Anyway, thanks for the library! Hope this helps improve it.

[kota65535]

@eropple fixed in 0.5.4, please try it.

[kota65535]

I've also added a usage in case of not merging arrays in README, hope this helps.