Added USD as a language + some queries

Added USD highlight unittests

Added USD indentation

Added USD indents.scm file

Added USD indent rules

Simplified USD highlight groups

Added explicit highlight groups

Added newline

Removed after/ftdetect/usda.lua

usd/indents.scm - Added inline comments explaining the nodes

Fixed USD highlight group unittests

Added indentation unittests

Simplified USD `@identifier` highlighting

Added USD documentation highlight group tests

Simplified USD highlight groups

Moved USD `@identifier` and `@namespace` highlights into one place

Removed and simplified tests/query/highlights/usd

Simplified tests/query/highlights/usd more

Removed trailing newline

Combined USD test files

Added `set filetype=usd` to minimal_init.lua

queries/usd/indents.scm

@@ -0,0 +1,26 @@
+[
+  (block)  ; The {}s in `def "foo" { ... Attributes / Prims here ... }`
+  (dictionary)  ; The {}s in `dictionary foo = { string "foo" = "bar" }`
+  (list)
+  (list_proxy)  ; [@foo.usda@, @bar.usda@]
+  (metadata)  ; ( anything = "goes-here" )
+  (prim_paths)  ; [</foo>, <../bar>]
+  (timeSamples)  ; The {}s in `int value.timeSamples = { 0: 1, -10: 10, ... }`
+  (tuple)
+  (variant_set_definition)  ; The {}s in `variantSet "foo" = { "vr1" { ... } "vr2" { ... } }`
+] @indent.begin
+
+(block "}" @indent.end)
+(dictionary "}" @indent.end)
+(list "]" @indent.end)
+(list_proxy "]" @indent.end)
+(metadata ")" @indent.end)
+(timeSamples "}" @indent.end)
+(tuple ")" @indent.end)
+(variant_set_definition "}" @indent.end)
+
+[
+  ")"
+  "]"
+  "}"
+] @indent.branch