docs: Add Caddyfile syntax highlighting (#41)

src/docs/markdown/quick-starts/caddyfile.md

@@ -8,7 +8,7 @@ Create a new text file named `Caddyfile` (no extension).
 
 The first thing to type in a Caddyfile is your site's address:
 
-```
+```caddy
 localhost
 ```
 
@@ -18,7 +18,7 @@ localhost
 
 Then hit enter and type what you want it to do, so it looks like this:
 
-```
+```caddy
 localhost
 
 respond "Hello, world!"
@@ -43,7 +43,7 @@ Hello, world!</code></pre>
 
 You can define multiple sites in a Caddyfile by wrapping them in curly braces `{ }`. Change your Caddyfile to be:
 
-```
+```caddy
 localhost {
 	respond "Hello, world!"
 }

src/docs/markdown/quick-starts/https.md

@@ -40,7 +40,7 @@ This is the most common way to get HTTPS.
 
 Create a file called `Caddyfile` (no extension) where the first line is your domain name, for example:
 
-```
+```caddy
 example.com
 
 respond "Hello, privacy!"

src/docs/markdown/quick-starts/reverse-proxy.md

@@ -36,7 +36,7 @@ Then make a request to [localhost](https://localhost) (or whatever address you s
 
 In the current working directory, create a file called `Caddyfile` with these contents:
 
-```
+```caddy
 localhost
 
 reverse_proxy 127.0.0.1:9000
@@ -50,7 +50,7 @@ You can then make a request to [https://localhost](https://localhost) to see it
 
 It's easy to change the proxy's address:
 
-```
+```caddy
 :2016
 
 reverse_proxy 127.0.0.1:9000

src/docs/markdown/quick-starts/static-files.md

@@ -41,7 +41,7 @@ You can use another folder as the site root:
 
 In the root of your site, create a file called `Caddyfile` with these contents:
 
-```
+```caddy
 localhost
 
 file_server
@@ -59,7 +59,7 @@ The [`file_server` directive](/docs/caddyfile/directives/file_server) has more o
 
 If you don't have an index file but you want to display a file listing, use the `browse` argument:
 
-```
+```caddy
 localhost
 
 file_server browse
@@ -67,7 +67,7 @@ file_server browse
 
 You can also use another folder as the site root:
 
-```
+```caddy
 localhost
 
 root * /home/me/mysite