doc: add Buffer.from(string) to functions that use buffer pool

Buffer.from(string) is one of the functions that may use the
pre-allocated buffer. It's mentioned in the description of
Buffer.from(array), but not in Buffer.from(string), or in the two other
places where functions that behave this way are listed, so this commit
adds those references.

doc/api/buffer.md

@@ -808,7 +808,7 @@ A `TypeError` will be thrown if `size` is not a number.
 The `Buffer` module pre-allocates an internal `Buffer` instance of
 size [`Buffer.poolSize`][] that is used as a pool for the fast allocation of new
 `Buffer` instances created using [`Buffer.allocUnsafe()`][], [`Buffer.from(array)`][],
-and [`Buffer.concat()`][] only when `size` is less than
+[`Buffer.from(string)`][], and [`Buffer.concat()`][] only when `size` is less than
 `Buffer.poolSize >>> 1` (floor of [`Buffer.poolSize`][] divided by two).
 
 Use of this pre-allocated internal memory pool is a key difference between
@@ -846,11 +846,11 @@ _may contain sensitive data_. Use [`buf.fill(0)`][`buf.fill()`] to initialize
 such `Buffer` instances with zeroes.
 
 When using [`Buffer.allocUnsafe()`][] to allocate new `Buffer` instances,
-allocations under 4 KiB are sliced from a single pre-allocated `Buffer`. This
-allows applications to avoid the garbage collection overhead of creating many
-individually allocated `Buffer` instances. This approach improves both
-performance and memory usage by eliminating the need to track and clean up as
-many individual `ArrayBuffer` objects.
+allocations less than `Buffer.poolSize >>> 1` (4KiB when default poolSize is used) are sliced
+from a single pre-allocated `Buffer`. This allows applications to avoid the
+garbage collection overhead of creating many individually allocated `Buffer`
+instances. This approach improves both performance and memory usage by
+eliminating the need to track and clean up as many individual `ArrayBuffer` objects.
 
 However, in the case where a developer may need to retain a small chunk of
 memory from a pool for an indeterminate amount of time, it may be appropriate
@@ -1390,6 +1390,9 @@ console.log(buf1.toString('latin1'));
 A `TypeError` will be thrown if `string` is not a string or another type
 appropriate for `Buffer.from()` variants.
 
+[`Buffer.from(string)`][] may also use the internal `Buffer` pool like
+[`Buffer.allocUnsafe()`][] does.
+
 ### Static method: `Buffer.isBuffer(obj)`
 
 <!-- YAML
@@ -5444,10 +5447,10 @@ to one of these new APIs._
   uninitialized, the allocated segment of memory might contain old data that is
   potentially sensitive.
 
-`Buffer` instances returned by [`Buffer.allocUnsafe()`][] and
-[`Buffer.from(array)`][] _may_ be allocated off a shared internal memory pool
-if `size` is less than or equal to half [`Buffer.poolSize`][]. Instances
-returned by [`Buffer.allocUnsafeSlow()`][] _never_ use the shared internal
+`Buffer` instances returned by [`Buffer.allocUnsafe()`][], [`Buffer.from(string)`][],
+[`Buffer.concat()`][] and [`Buffer.from(array)`][] _may_ be allocated off a shared
+internal memory pool if `size` is less than or equal to half [`Buffer.poolSize`][].
+Instances returned by [`Buffer.allocUnsafeSlow()`][] _never_ use the shared internal
 memory pool.
 
 ### The `--zero-fill-buffers` command-line option