Fix smartstraps redirects using index.html instead of bare trailing slashes

Bare trailing-slash redirect paths like /guides/smartstraps/ cause a
conflict during Jekyll write phase — the path gets created as a file
by one redirect page, then a sub-path redirect tries to mkdir_p it as
a directory. Using explicit index.html avoids this.

Author: jplexer

source/_data/redirects.yaml

@@ -2656,19 +2656,19 @@
  - /guides/hardware/talking-to-smartstraps/index.html
  - /guides/
 -
- - /guides/smartstraps/
+ - /guides/smartstraps/index.html
  - /guides/
 -
- - /guides/smartstraps/smartstrap-hardware/
+ - /guides/smartstraps/smartstrap-hardware/index.html
  - /guides/
 -
- - /guides/smartstraps/smartstrap-protocol/
+ - /guides/smartstraps/smartstrap-protocol/index.html
  - /guides/
 -
- - /guides/smartstraps/talking-to-pebble/
+ - /guides/smartstraps/talking-to-pebble/index.html
  - /guides/
 -
- - /guides/smartstraps/talking-to-smartstraps/
+ - /guides/smartstraps/talking-to-smartstraps/index.html
  - /guides/
 -
  - /guides/timeline/index.html