(PowerShellGH-1428) Make region folding case insensitive and parse whitespace correctly

Previously the code folding feature would fail to find region blocks starting
with `Region` or ending with `EndRegion`.  This was due to the regex only
looking for lower case.  This commit updates the start and end region
detection to use a similar regex to that of the VS Code default, defined in
microsoft/vscode@64186b0

Previously the code folding had trouble detecting the beginning of comment
blocks and regions which were not indented.  This was due to the empty line
regex expecting at least one whitespace character to be considered "an empty
line".  This commit modifies the empty line regex to also allow an empty string
which is indeed, an empty line.

Author: glennsarti

src/features/Folding.ts

@@ -354,7 +354,7 @@ export class FoldingProvider implements vscode.FoldingRangeProvider {
     ): ILineNumberRangeList {
         const result = [];
 
-        const emptyLine = /^[\s]+$/;
+        const emptyLine = /^\s*$/;
 
         let startLine: number = -1;
         let nextLine: number = -1;
@@ -421,9 +421,9 @@ export class FoldingProvider implements vscode.FoldingRangeProvider {
     ): ITokenList {
         const result = [];
 
-        const emptyLine = /^[\s]+$/;
-        const startRegionText = /^#\s*region\b/;
-        const endRegionText = /^#\s*endregion\b/;
+        const emptyLine = /^\s*$/;
+        const startRegionText = /^#\s*region\b/i;
+        const endRegionText = /^#\s*endregion\b/i;
 
         tokens.forEach((token) => {
             if (token.scopes.indexOf("punctuation.definition.comment.powershell") !== -1) {

test/features/folding.test.ts

@@ -38,16 +38,19 @@ suite("Features", () => {
 
         suite("For a single document", async () => {
             const expectedFoldingRegions = [
-                { start: 1,  end: 6,  kind: 1 },
-                { start: 7,  end: 51, kind: 3 },
-                { start: 8,  end: 13, kind: 1 },
-                { start: 14, end: 17, kind: 3 },
-                { start: 19, end: 22, kind: 3 },
-                { start: 26, end: 28, kind: 1 },
-                { start: 30, end: 40, kind: 3 },
-                { start: 32, end: 36, kind: 3 },
-                { start: 42, end: 44, kind: 3 },
-                { start: 47, end: 50, kind: 3 },
+                { start: 0,  end: 4,  kind: 3 },
+                { start: 1,  end: 3,  kind: 1 },
+                { start: 6,  end: 8,  kind: 3 },
+                { start: 10, end: 15, kind: 1 },
+                { start: 16, end: 60, kind: 3 },
+                { start: 17, end: 22, kind: 1 },
+                { start: 23, end: 26, kind: 3 },
+                { start: 28, end: 31, kind: 3 },
+                { start: 35, end: 37, kind: 1 },
+                { start: 39, end: 49, kind: 3 },
+                { start: 41, end: 45, kind: 3 },
+                { start: 51, end: 53, kind: 3 },
+                { start: 56, end: 59, kind: 3 },
             ];
 
             test("Can detect all of the foldable regions in a document with CRLF line endings", async () => {

test/fixtures/folding-crlf.ps1

@@ -1,3 +1,12 @@
+#RegIon This should fold
+<#
+Nested different comment types.  This should fold
+#>
+#EnDReGion
+
+# region This should also fold
+$shouldFold = $true
+#    endRegion
 function short-func-not-fold {};
 <#
 .SYNOPSIS

test/fixtures/folding-lf.ps1

@@ -1,3 +1,12 @@
+#RegIon This should fold
+<#
+Nested different comment types.  This should fold
+#>
+#EnDReGion
+
+# region This should also fold
+$shouldFold = $true
+#    endRegion
 function short-func-not-fold {};
 <#
 .SYNOPSIS