Added two html alert template examples (#8360)

Added two html alert template examples. Asked pii100 for permission to include his and he said ok.
Included my html service alert check that includes service_message.
Added a note for html and graphs. I believe most people will find it useful on this page.

doc/Alerting/Templates.md

@@ -191,6 +191,56 @@ Conditional formatting example, will display a link to the host in email or just
 
 Note the use of double-quotes.  Single quotes (`'`) in templates will be escaped (replaced with `\'`) in the output and should therefore be avoided.
 
+## Examples HTML
+
+Note: To use HTML emails you must set HTML email to Yes in the WebUI under Global Settings > Alerting Settings > Email transport > Use HTML emails
+
+Note: To include Graphs you must enable unauthorized graphs in config.php. Allow_unauth_graphs_cidr is optional, but more secure.
+```
+$config['allow_unauth_graphs_cidr'] = array(127.0.0.1/32');  
+$config['allow_unauth_graphs'] = true;
+```
+
+Service Alert:
+```<div style="font-family:Helvetica;">
+<h2>{if %state == 1}<span style="color:red;">%severity{/if}
+{if %state == 2}<span style="color:goldenrod;">acknowledged{/if}</span>
+{if %state == 3}<span style="color:green;">recovering{/if}</span>
+{if %state == 0}<span style="color:green;">recovered{/if}</span>
+</h2>
+<b>Host:</b> %hostname<br>
+<b>Duration:</b> %elapsed<br>
+<br>
+
+{if %faults}                                                                                       
+{foreach %faults}<b>%value.service_desc - %value.service_type</b><br>                                         
+%value.service_message<br>
+<br>                                                                                         
+{/foreach}                                                                                                             
+{/if}
+</div>
+```
+
+Processor Alert with Graph:
+```%title <br>
+Severity: %severity  <br>
+{if %state == 0}Time elapsed: %elapsed{/if}
+Timestamp: %timestamp <br>
+Alert-ID: %id <br>
+Rule: {if %name}%name{else}%rule{/if} <br>
+{if %faults}Faults:
+{foreach %faults}
+#%key: %value.string <br>
+{/foreach}
+{if %faults}<b>Faults:</b><br>
+{foreach %faults}<img src="https://server/graph.php?device=%value.device_id&type=device_processor&width=459&height=213&lazy_w=552&from=end-72h%22/%3E<br>
+https://server/graphs/id=%value.device_id/type=device_processor/<br>
+{/foreach}
+Template: CPU alert <br>
+{/if}
+{/if}
+```
+
 ## Included
 
 We include a few templates for you to use, these are specific to the type of alert rules you are creating. For example if you create a rule that would alert on BGP sessions then you can