Describe the solution you'd like
Several tech mods add a dust form of obsidian obtained via crushing, it would be nice to be able to melt these dusts in the smeltery

Additional context
Any items with the forge:dusts/obsidian tag would be melted into 250mb of molten obsidian

Versions:

• Minecraft: 1.16.5
• Forge: 36.1.4
• Mantle: 1.6.92
• Tinkers Construct: 3.0.3.136

Confirm below that this enhancement is not covered on the roadmap or "Whats New?"
Confirmed

Added in 3.0.3.152

Generally speaking, dusts seem to be equivalent to somewhere between 1 and 4 units of whatever material they are a dust of. The exact number varies from one mod to another, so I'm not fully settled on using the ratio of 4 dust<->1 obsidian.
In any case, if we go with that ratio, the JSON we'd want to generate for this should end up looking something like the following:

{
  "type": "tconstruct:melting",
  "conditions": [
    {
      "value": {
        "tag": "forge:dusts/obsidian",
        "type": "forge:tag_empty"
      },
      "type": "forge:not"
    }
  ],
  "ingredient": {
    "tag": "forge:dusts/obsidian"
  },
  "result": {
    "fluid": "tconstruct:molten_obsidian",
    "amount": 250
  },
  "temperature": 1000,
  "time": 66
}

This could end up in a new file at src/generated/resources/data/tconstruct/recipes/smeltery/melting/obsidian_dust.json

I believe we could generate such a file by adding the following snippet into src/main/java/slimeknights/tconstruct/smeltery/data/SmelteryRecipeProvider.java:addMeltingRecipes, probably somewhere next to the existing obsidian-related melting recipes.

    MeltingRecipeBuilder.melting(Ingredient.fromTag(getTag("forge", "dusts/obsidian")), TinkerFluids.moltenObsidian.get(), MaterialValues.SLIMEBALL, 0.5f)
	                    .build(withCondition(consumer, tagCondition("dusts/obsidian")), location(folder + "obsidian_dust"));

If this is something the main developers agree on implementing, and that snippet looks like it should do the trick, I'd be happy to throw it into a quick PR.

Even if it doesn't end up included in the mod, you should still be able to use the JSON snippet from above to add the recipe yourself with a custom datapack.

We have a helper function to generate such recipes (used for mod compat metals). Probably easier if I add it directly as it would take as much time to implement as to review a PR