Add ubiquitous doodle placeholder

[franciscosmit04-eng]

Adds the requested empty ubiquitous-doodle.md placeholder at the repository root.

[franciscosmit04-eng]

#include <nvtx3/nvToolsExtPayload.h>
#include <nvtx3/nvToolsExtPayloadHelper.h>

NVTX_DEFINE_STRUCT_WITH_SCHEMA_AND_REGISTER(domain, Step, "training.step",
NVTX_PAYLOAD_ENTRIES(
(uint64_t, iteration, TYPE_UINT64, "Training step index"),
(float, loss, TYPE_FLOAT, "Training loss")
)
)

Step value = {42, 0.125f};
nvtxPayloadData_t pld = {Step_schemaId, sizeof(value), &value};
nvtxMarkPayload(domain, &pld, 1);