patch 9.1.0655: filetype: goaccess config file not recognized

Problem:  filetype: goaccess config file not recognized
Solution: detect 'goaccess.conf' as goaccess filetype, also
          include a basic syntax and ftplugin (Adam Monsen)

Add syntax highlighting for GoAccess configuration file.

GoAccess is a real-time web log analyzer and interactive viewer that
runs in a terminal in *nix systems or through your browser.

GoAccess home page: https://goaccess.io

closes: #15414

Signed-off-by: Adam Monsen <haircut@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/goaccess.vim

@@ -0,0 +1,34 @@
+" Vim syntax file
+" Language: GoAccess configuration
+" Maintainer: Adam Monsen <haircut@gmail.com>
+" Last Change: 2024 Aug 1
+" Remark: see https://goaccess.io/man#configuration
+"
+" The GoAccess configuration file syntax is line-separated settings. Settings
+" are space-separated key value pairs. Comments are any line starting with a
+" hash mark.
+" Example: https://github.com/allinurl/goaccess/blob/master/config/goaccess.conf
+"
+" This syntax definition supports todo/fixme highlighting in comments, and
+" special (Keyword) highlighting if a setting's value is 'true' or 'false'.
+"
+" TODO: a value is required, so use extreme highlighting (e.g. bright red
+" background) if a setting is missing a value.
+
+if exists("b:current_syntax")
+  finish
+endif
+
+syn match goaccessSettingName '^[a-z-]\+' nextgroup=goaccessSettingValue
+syn match goaccessSettingValue '\s\+.\+$' contains=goaccessKeyword
+syn match goaccessComment "^#.*$" contains=goaccessTodo,@Spell
+syn keyword goaccessTodo TODO FIXME contained
+syn keyword goaccessKeyword true false contained
+
+hi def link goaccessSettingName Type
+hi def link goaccessSettingValue String
+hi def link goaccessComment Comment
+hi def link goaccessTodo Todo
+hi def link goaccessKeyword Keyword
+
+let b:current_syntax = "goaccess"