Escape periods in path

Unescaped periods in things like paths in tables can trigger failed man
page builds.

Signed-off-by: Brent Baude <[email protected]>

Author: baude

docs/source/markdown/podman-systemd.unit.5.md

@@ -1730,7 +1730,7 @@ Valid options for `[Build]` are listed below:
 | ForceRM=false                       | --force-rm=false                            |
 | GlobalArgs=--log-level=debug        | --log-level=debug                           |
 | GroupAdd=keep-groups                | --group-add=keep-groups                     |
-| IgnoreFile=/path/to/.customignore   | --ignorefile=/path/to/.customignore         |
+| IgnoreFile=/path/to/\.customignore  | --ignorefile=/path/to/\.customignore        |
 | ImageTag=localhost/imagename        | --tag=localhost/imagename                   |
 | Label=label                         | --label=label                               |
 | Network=host                        | --network=host                              |