add FiberHandle module, for holding a reference to a running fiber (#…

…2524)

.changeset/brave-eggs-allow.md

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+---
+"effect": minor
+---
+
+close FiberHandle/FiberSet/FiberMap when it is released
+
+When they are closed, fibers can no longer be added to them.

.changeset/odd-ears-build.md

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+---
+"effect": patch
+---
+
+add FiberMap.has/unsafeHas api

.changeset/sweet-apples-applaud.md

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+---
+"effect": patch
+---
+
+add FiberHandle module, for holding a reference to a running fiber
+
+```ts
+import { Effect, FiberHandle } from "effect"
+
+Effect.gen(function* (_) {
+  const handle = yield* _(FiberHandle.make())
+
+  // run some effects
+  yield* _(FiberHandle.run(handle, Effect.never))
+  // this will interrupt the previous fiber
+  yield* _(FiberHandle.run(handle, Effect.never))
+  // this will not run, as a fiber is already running
+  yield* _(FiberHandle.run(handle, Effect.never, { onlyIfMissing: true }))
+
+  yield* _(Effect.sleep(1000))
+}).pipe(
+  Effect.scoped // The fiber will be interrupted when the scope is closed
+)
+```