Add xSPSearchCrawlerImpactRule resource about sharepointdsc

[mrpullen]

Looking at New-SPEnterpriseSearchSiteHitRule

seems like we could do something like

xSPSearchCrawlerImpactRule ThrottleIntranetCrawl
{
ServiceAppName = "Enterprise Search Service Application"
Site = "https://intranet.sharepoint.contoso.com"
Behavior = "RequestLimit" // ValidateSet("RequestLimit","WaitTime")
HitRate = 8  // Request Limit or Wait Time in seconds.
}

or something like this, where we only allow them to specify either RequestLimit or WaitTime.

xSPSearchCrawlerImpactRule ThrottleIntranetCrawl
{
ServiceAppName = "Enterprise Search Service Application"
Site = "https://intranet.sharepoint.contoso.com"
RequestLimit = 8
WaitTime = 60  
}

[ykuijs]

Resource created in PR 531