doc: Update release steps for version.cache and deprecated tag

doc/release_steps.txt

@@ -53,6 +53,8 @@ the 'ns-3.x' module may need some indirection to fetch ns-3-dev in its place.
    - ./download.py
    - cd ns-3-dev
    - edit VERSION such as "ns-3.31.rc1" (DO NOT commit this change to ns-3-dev)
+   - generate a version.cache file via './ns3 configure --enable-build-version'
+   - remove other files generated by the previous step ('./ns3 clean')
    - cd ../bake
    - copy over the modified bakeconf.xml that is being tested
    - cd ..
@@ -113,10 +115,26 @@ bake commit ba47854c (July 14, 2021).
    - ./download.py
    - cd ns-3-dev
    - git checkout -b 'ns-3.x-release' ns-3.x
+   - ./ns3 configure --enable-build-version
+   - ./ns3 clean
    - cd ../
    - ./dist.py (notice we did not build here)
    - this will create an ns-allinone-3.x.tar.bz2 tarball
 
+Make sure that the version.cache file included in the source archive looks
+something like the below example:
+
+CLOSEST_TAG = '"ns-3.36.1"'
+VERSION_COMMIT_HASH = '"g7004d1a66"'
+VERSION_DIRTY_FLAG = '0'
+VERSION_MAJOR = '3'
+VERSION_MINOR = '36'
+VERSION_PATCH = '1'
+VERSION_RELEASE_CANDIDATE = '""'
+VERSION_TAG = '"ns-3.36.1"'
+VERSION_TAG_DISTANCE = '0'
+VERSION_BUILD_PROFILE = 'relwithdebinfo
+
 4.  Test this tarball on at least one system
    - check that ns-3-allinone build.py works
    - check that bake ns-3.x and ns-allinone-3.x targets work
@@ -197,6 +215,16 @@ Announcing
 First, create skeletal sections in CHANGES.html and RELEASE_NOTES.md to
 start collecting inputs for the ns-3.(x+1) release.
 
+Next, add a new deprecated tag for the new release cycle, similar to
+commit 643d06ed9:
+
++/**
++ * \ingroup core
++ * \def NS_DEPRECATED_3_37
++ * Tag for things deprecated in version ns-3.37.
++ */
++#define NS_DEPRECATED_3_37(msg) NS_DEPRECATED(msg)
+
 The project may decide to make incremental, bug-fix releases from
 time to time, with a minor version number (e.g. ns-3.36.1).  To do
 this, changesets may be cherry-picked from ns-3-dev and added to