feat: Add not conditions assertions

Based on PHP-SDK discussion featurevisor/featurevisor-php#8 (comment)

Author: Greg0

examples/example-1/segments/notChromeV1.yml

@@ -0,0 +1,10 @@
+description: Not Chrome v1 browser
+conditions:
+  - not:
+      - attribute: browser.name
+        operator: equals
+        value: chrome
+      - attribute: browser.version
+        operator: equals
+        value: "1.0"
+

examples/example-1/tests/segments/notChromeV1.spec.yml

@@ -0,0 +1,30 @@
+segment: notChromeV1
+assertions:
+  ##
+  # Match
+  #
+  - context:
+      browser:
+        name: chrome
+    expectedToMatch: true
+
+  - context:
+      browser:
+        name: chrome
+        version: 2.0
+    expectedToMatch: true
+
+  - context:
+      browser:
+        name: firefox
+        version: 1.0
+    expectedToMatch: true
+
+  ##
+  # Not match
+  #
+  - context:
+      browser:
+        name: chrome
+        version: 1.0
+    expectedToMatch: false