feat(expect): add more methods

tests/.snapshots/success.txt

@@ -5,21 +5,16 @@
    PASS  Tests\Expect\ToBe
   ✓ strict comparisons
   ✓ failures
-  ✓ not failures
-
-   PASS  Tests\Expect\thatDirectoryExists
-  ✓ pass
-  ✓ failures
-  ✓ not failures
-
-   PASS  Tests\Expect\thatDirectoryIsReadable
-  ✓ pass
-  ✓ failures
   ✓ not failures
 
    PASS  Tests\Expect\toBeEmpty
   ✓ pass
   ✓ failures
+  ✓ not failures
+
+   PASS  Tests\Expect\toBeExistingDirectory
+  ✓ pass
+  ✓ failures
   ✓ not failures
 
    PASS  Tests\Expect\toBeFalse
@@ -45,6 +40,16 @@
    PASS  Tests\Expect\toBeLessThanOrEqual
   ✓ passes
   ✓ failures
+  ✓ not failures
+
+   PASS  Tests\Expect\toBeReadableDirectory
+  ✓ pass
+  ✓ failures
+  ✓ not failures
+
+   PASS  Tests\Expect\toBeWritableDirectory
+  ✓ pass
+  ✓ failures
   ✓ not failures
 
    PASS  Tests\Expect\toContain
@@ -262,5 +267,5 @@
    WARN  Tests\Visual\Success
   - visual snapshot of test suite on success
 
-  Tests:  6 skipped, 153 passed
-  Time:   4.35s
+  Tests:  6 skipped, 156 passed
+  Time:   4.42s