Set up some regular sync between wire-cell-toolkit/spng branch and this repo, add this repo to deepwiki

[brettviren]

[brettviren]

Note, WCT master branch is indexed already: https://deepwiki.com/WireCell/wire-cell-toolkit

However, there is no way to tell deepwiki to index a branch. However, since we use the git subrepo method to allow sync between this repo and the spng branch, we could "trick" deepwiki to show the spng part.