Update naming scheme wiki entry. (#139)

We had a capitalization scheme wiki entry, but hadn't documented our
standard of using underscores instead of dashes for multi-word package
names. This PR converts the capitalization scheme into a naming scheme,
which also documents the underscore usage.

For some historic discussion there's e.g. [this Zulip
thread](https://xi.zulipchat.com/#narrow/stream/354396-xilem/topic/.E2.9C.94.20Crate.20naming).
Otherwise, there's just the fact that all our modern packages are named
as such, e.g. `vello_hybrid`, `masonry_core`, etc.

Author: xStrom

content/wiki/capitalization_scheme.md

@@ -0,0 +1,12 @@
++++
+title = "Naming scheme for Linebender projects"
++++
+
+All Linebender projects should follow this naming scheme:
+
+- The project name uses title case and spaces for word separation, e.g. *Vello* or *Vello Hybrid*.
+- The package name uses lower case and underscores for word separation, e.g. `vello` or `vello_hybrid`.
+- When referring to the package, e.g. in relation to crates.io, use backticks to put the name in a codeblock, e.g. `vello`.
+- When referring to the GitHub repository, make it a link, e.g. [vello#1](https://github.com/linebender/vello/pull/1).
+
+Feel free to correct any documentation you see that doesn't yet follow this scheme, unless the project is explicitly discontinued or in maintenance mode (eg Xi-Editor, Piet).