contrib: rename initrd READMEs to README.md

It's an unhelpful naming scheme and one that breaks GitHub autoreadme.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13017

contrib/dracut/Makefile.am

@@ -3,4 +3,4 @@ include $(top_srcdir)/config/Shellcheck.am
 SUBDIRS = 02zfsexpandknowledge 90zfs
 SHELLCHECKDIRS = $(SUBDIRS)
 
-EXTRA_DIST = README.dracut.markdown
+EXTRA_DIST = README.md

contrib/initramfs/Makefile.am

@@ -8,5 +8,4 @@ dist_initrd_SCRIPTS = \
 SUBDIRS = conf.d conf-hooks.d hooks scripts
 SHELLCHECKDIRS = hooks scripts
 
-EXTRA_DIST = \
-	README.initramfs.markdown
+EXTRA_DIST = README.md

rpm/generic/zfs.spec.in

@@ -540,7 +540,7 @@ systemctl --system daemon-reload >/dev/null || true
 %{_datadir}/%{name}/*.sh
 
 %files dracut
-%doc contrib/dracut/README.dracut.markdown
+%doc contrib/dracut/README.md
 %{_dracutdir}/modules.d/*
 
 %if %{with pyzfs}
@@ -554,7 +554,7 @@ systemctl --system daemon-reload >/dev/null || true
 
 %if 0%{?_initramfs}
 %files initramfs
-%doc contrib/initramfs/README.initramfs.markdown
+%doc contrib/initramfs/README.md
 /usr/share/initramfs-tools/*
 %else
 # Since we're not building the initramfs package,