Fix decision filename (#186)

proposals/README.md

@@ -36,6 +36,7 @@ request:
 -   [0083 - In-progress design overview](p0083.md)
     -   [Decision](p0083_decision.md)
 -   [0107 - Code and name organization](p0107.md)
+    -   [Decision](p0107_decision.md)
 -   [0120 - Add idiomatic code performance and developer-facing docs to goals](p0120.md)
     -   [Decision](p0120_decision.md)
 -   [0142 - Unicode source files](p0142.md)