Add an initial RELNOTES file.

The intent is to provide a convenient location to document changes
that are relevant to users of binary FreeBSD distributions, in contrast
with UPDATING, which exists to document caveats for users who build
FreeBSD from source.

This complements the "Relnotes:" tag in commit messages by providing a
place to document the change in more detail, or in case a "Relnotes:"
tag was accidentally omitted.  In particular, "Relnotes:" should be
used if you do not intend to document the change in RELNOTES for some
reason.

Changes to the file should not be MFCed.  For now the file will exist
only in head, but may be updated via direct commits to stable branches
depending on how things go.

I took the liberty of pre-populating the file with some recent release
notes-worthy changes.

Reviewed by:	ian (earlier version)
Discussed with:	cy, gjb, imp, rgrimes
Differential Revision:	https://reviews.freebsd.org/D20762

RELNOTES

@@ -0,0 +1,34 @@
+Release notes for FreeBSD 13.0.
+
+This file describes new user-visible features, changes and updates relevant to
+users of binary FreeBSD releases.  Each entry should describe the change in no
+more than several sentences and should reference manual pages where an
+interested user can find more information.  Entries should wrap after 80
+columns.  Each entry should begin with one or more commit IDs on one line,
+specified as a comma separated list and/or range, followed by a colon and a
+newline.  Entries should be separated by a newline.
+
+Changes to this file should not be MFCed.
+
+r349352:
+	nand(4) and related components have been removed.
+
+r349349:
+	The UEFI loader now supports HTTP boot.
+
+r349335:
+	bhyve(8) now implements a High Definition Audio (HDA) driver, allowing
+	guests to play to and record audio data from the host.
+
+r349286:
+	swapon(8) can now erase a swap device immediately before enabling it,
+	similar to newfs(8)'s -E option.  This behaviour can be specified by
+	adding -E to swapon(8)'s command-line parameters, or by adding the
+	"trimonce" option to a swap device's /etc/fstab entry.
+
+r347908-r347923:
+	The following network drivers have been removed: bm(4), cs(4), de(4),
+	ed(4), ep(4), ex(4), fe(4), pcn(4), sf(4), sn(4), tl(4), tx(4), txp(4),
+	vx(4), wb(4), xe(4).
+
+$FreeBSD$