process: Backfill missing Version headers

…for BIPs that have a Changelog section that mentions a version.
BIP 1 and BIP 340 have Changelog sections, but do not define versions.

bip-0374.mediawiki

@@ -11,6 +11,7 @@
   License: BSD-2-Clause
   Discussion: https://gist.github.com/andrewtoth/df97c3260cc8d12f09d3855ee61322ea
               https://groups.google.com/g/bitcoindev/c/MezoKV5md7s
+  Version: 0.2.0
 </pre>
 
 == Introduction ==