[BETA] Add heuristic scheme

This is not enabled by default.
If you wish to use it, add following snippet to popup.html.

```
<option value="Heuristic">Heuristic</option>
```

python/schemes/Heuristic.py

@@ -0,0 +1,59 @@
+import re
+def replaceRequest(payload):
+    challengeB64 = base64.b64encode(challenge).decode()
+    challengeArr = str(list(challenge))
+
+    # Trying decode payload, challenge might be raw bytes if it failed
+    try:
+        decodedPayload = payload.decode()
+    except:
+        return challenge
+
+    # Challenge might be JSON/XML stored B64-encoded string
+    replaced = decodedPayload.replace(r"(?<=(\"|\'|>))CAES.*?(?=(\"|\'|<))", challengeB64).replace(r"(?<=(\"|\'|>))CAQ=(?=(\"|\'|<))", challengeB64)
+    if(decodedPayload != replaced):
+        return replaced
+
+    # Challenge might be raw B64-encoded string
+    replaced = decodedPayload.replace(r"^CAES.*?=$", challengeB64).replace(r"^CAQ=$", challengeB64)
+    if(decodedPayload != replaced):
+        return replaced
+
+    # Challenge might be Uint8Array
+    replaced = decodedPayload.replace(r"\[0?8 ?, ?0?1 ?, ?[0-9 ,]*?\]", challengeArr).replace(r"\[0?8 ?, ?0?4]", challengeArr)
+    if(decodedPayload != replaced):
+        return replaced
+
+
+def findLicense(response):
+    # Trying decode response, license might be raw bytes if it failed
+    try:
+        decodedResponse = response.decode()
+    except:
+        return response
+
+    # License might be JSON/XML stored B64-encoded string
+    try:
+        return re.search(r"(?<=(\"|\'|>))CAIS.*?(?=(\"|\'|<))", decodedResponse).group()
+    except:
+        pass
+
+    # License might be raw B64-encoded string
+    try:
+        return re.search(r"^CAIS.*?=$", decodedResponse).group()
+    except:
+        pass
+
+    # License might be Uint8Array
+    try:
+        foundStr = re.search(r"\[0?8 ?, ?0?2 ?, ?[0-9 ,]*?\]", decodedResponse).group()
+        return bytes(json.loads(foundStr))
+    except:
+        pass
+
+
+payload = loadBody("blob")
+payload = replaceRequest(payload)
+
+response = await corsFetch(licUrl, "POST", licHeaders, payload, "blob")
+licence = findLicense(response)