Fix long option format on docs.podman.io

Escape the two dashes, otherwise they are combined into one long dash.
I tested that this change is safe and still renders correctly on github
and with the man pages.

This commit also contains a small change to make it build locally.
Assuming you have the dependencies installed you can do:
```
cd docs
make html
```
Preview the html files in docs/build/html with
`python -m http.server 8000 --directory build/html`.

Fixes containers/podman.io#373

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

1 files changed, 3 insertions, 3 deletions

diff --git a/docs/source/markdown/podman-logout.1.md b/docs/source/markdown/podman-logout.1.md
index c35c4856b..caa8c9021 100644
--- a/docs/source/markdown/podman-logout.1.md
+++ b/docs/source/markdown/podman-logout.1.md
@@ -21,18 +21,18 @@ All the cached credentials can be removed by setting the **all** flag.
 
 ## OPTIONS
 
-#### **--authfile**=*path*
+#### **\-\-authfile**=*path*
 
 Path of the authentication file. Default is ${XDG\_RUNTIME\_DIR}/containers/auth.json.
 
 Note: You can also override the default path of the authentication file by setting the REGISTRY\_AUTH\_FILE
 environment variable. `export REGISTRY_AUTH_FILE=path`
 
-#### **--all**, **-a**
+#### **\-\-all**, **-a**
 
 Remove the cached credentials for all registries in the auth file
 
-#### **--help**, **-h**
+#### **\-\-help**, **-h**
 
 Print usage statement