[Varnish] #974: Add new ESI syntax to the upgrade page

[Varnish]

#974: Add new ESI syntax to the upgrade page
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 Reporter:  smerrill  |        Type:  documentation
   Status:  new       |    Priority:  low          
Milestone:            |   Component:  documentation
  Version:  3.0.0     |    Severity:  minor        
 Keywords:            |  
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 I was helping a friend upgrade to 3.0, and https://www.varnish-
 cache.org/docs/trunk/installation/upgrade.html is great, but it's missing
 the new ESI keyword.

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Ticket URL: <http://varnish-cache.org/trac/ticket/974>
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