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, 5 insertions, 5 deletions

diff --git a/docs/source/markdown/podman-volume-rm.1.md b/docs/source/markdown/podman-volume-rm.1.md
index c066d1c6e..2727ea640 100644
--- a/docs/source/markdown/podman-volume-rm.1.md
+++ b/docs/source/markdown/podman-volume-rm.1.md
@@ -9,22 +9,22 @@ podman\-volume\-rm - Remove one or more volumes
 ## DESCRIPTION
 
 Removes one or more volumes. Only volumes that are not being used will be removed.
-If a volume is being used by a container, an error will be returned unless the **--force**
-flag is being used. To remove all volumes, use the **--all** flag.
+If a volume is being used by a container, an error will be returned unless the **\-\-force**
+flag is being used. To remove all volumes, use the **\-\-all** flag.
 Volumes can be removed individually by providing their full name or a unique partial name.
 
 ## OPTIONS
 
-#### **--all**, **-a**
+#### **\-\-all**, **-a**
 
 Remove all volumes.
 
-#### **--force**, **-f**
+#### **\-\-force**, **-f**
 
 Remove a volume by force.
 If it is being used by containers, the containers will be removed first.
 
-#### **--help**
+#### **\-\-help**
 
 Print usage statement