[EXT] Explanation about update to luatex received via tlmgr

[Karl Berry]

    https://www.tug.org/svn/texlive/trunk/

Online repo browsing should be back now.

    mm> the documentation for LuaTeX has now
    been updated (with files like
    Master/texmf-dist/doc/luatex/base/luatex-lua.tex, which also triggered
    a "package update" with "fake version update"), 
    
Right.

    but the binary itself wasn't changed?

Luigi commits doc updates when he commits source updates, independent of
binary updates.  --best, karl.