Update RFC 0430 to allow underscores between numbers in CamelCase names

See rust-lang#46907

Author: pyfisch

text/0430-finalizing-naming-conventions.md

@@ -46,6 +46,9 @@ precisely, the proposed (and mostly followed) conventions are:
 In `UpperCamelCase`, acronyms count as one word: use `Uuid` rather than
 `UUID`.  In `snake_case`, acronyms are lower-cased: `is_xid_start`.
 
+In `UpperCamelCase` names multiple numbers can be separated by a `_`
+for clarity: `Windows10_1709` instead of `Windows101709`.
+
 In `snake_case` or `SCREAMING_SNAKE_CASE`, a "word" should never
 consist of a single letter unless it is the last "word". So, we have
 `btree_map` rather than `b_tree_map`, but `PI_2` rather than `PI2`.