chore: gitignore example binaries by extension, not by the name 'main'

The rule was examples/**/main.exe | main | main.app, which assumed every
example compiles to `main`. The world-viewer compiles to world-viewer.exe,
so it matched nothing, got committed at 26 MB, and was one merge away from
being in main's history forever (where deleting it later would not have
removed it -- the blob stays reachable).

Match by extension instead. The .exe itself is dropped from this branch's
commits in the same push, so the blob never reaches main.

Author: Ralph Kuepper

.gitignore

@@ -76,7 +76,12 @@ examples/intel-sponza/assets/outdoor.hdr
 *.actual.png
 
 # Compiled example binaries — build artifacts, never commit.
-examples/**/main.exe
+# Match by EXTENSION, not by the name `main`: this list used to be main.exe /
+# main / main.app, which assumed every example compiles to `main`. The
+# world-viewer compiles to world-viewer.exe, sailed straight through, and a
+# 26 MB binary was committed and very nearly merged to main.
+examples/**/*.exe
+examples/**/*.pdb
 examples/**/main
 examples/**/main.app