Add support for syntax-based folding

Regions, comment blocks, and heredocs can now be folded.
Additionally, Sublime Text now indexes region names as symbols.

Author: matteocoder

Fold.tmPreferences

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<plist version="1.0">
+<dict>
+    <key>scope</key>
+    <string>source.powershell</string>
+    <key>settings</key>
+    <dict>
+        <key>foldScopes</key>
+        <array>
+            <dict>
+                <key>begin</key>
+                <string>punctuation.section.block.begin</string>
+                <key>end</key>
+                <string>punctuation.section.block.end</string>
+            </dict>
+            <dict>
+                <key>begin</key>
+                <string>punctuation.definition.comment.block.begin</string>
+                <key>end</key>
+                <string>punctuation.definition.comment.block.end</string>
+            </dict>
+            <dict>
+                <key>begin</key>
+                <string>punctuation.definition.string.begin</string>
+                <key>end</key>
+                <string>punctuation.definition.string.end</string>
+            </dict>
+        </array>
+    </dict>
+</dict>
+</plist>

PowerShell.sublime-syntax

@@ -35,6 +35,7 @@ contexts:
       pop: true
 
   main:
+    - include: regions
     - include: comments
     - include: expressions
 
@@ -808,3 +809,17 @@ contexts:
         - match: (?=\()
           pop: true
         - include: comment-line
+
+  regions:
+    - match: ^(#region\s*(.*))$
+      captures:
+        # Applying the punctuation.section.block.begin scope to the entire pattern
+        # allows Sublime Text to show the region name when it is folded.
+        1: punctuation.section.block.begin.powershell comment.line.powershell
+        2: meta.toc-list.powershell
+    - match: ^#endregion
+      scope: punctuation.section.block.end.powershell comment.line.powershell
+      push:
+        - meta_content_scope: comment.line.powershell
+        - include: pop-at-newline
+        - include: comment-embedded-docs

Tests/syntax_test_PowerShell.ps1

@@ -469,6 +469,11 @@ There is no @platting here!
 "@
 # <- string.quoted.double.heredoc
  # <- string.quoted.double.heredoc
+@'
+#<- meta.string string.quoted.single.heredoc punctuation.definition.string.begin
+A 'single quoted' "heredoc"
+'@
+#<- meta.string string.quoted.single.heredoc punctuation.definition.string.end
 
 # Numeric constants
 
@@ -1805,3 +1810,10 @@ function get-number {}
 #<- comment.block comment.documentation.embedded punctuation.definition.keyword.documentation
 #^^^^^^^^^^^^ keyword.other.documentation
 #>
+
+#region Test
+#<- punctuation.section.block.begin comment.line
+#       ^^^^ meta.toc-list
+#endregion (Text after #endregion is optional, but the ISE marks it as a comment as well)
+#<- punctuation.section.block.end comment.line
+#          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line