CI: add typos config for ignoring Base64 (#1735)

Uses a regex to detect strings that appear to be sequences of
Base64-encoded characters, and re-enables the lint for the JWK
implementation in `elliptic-curve`

Author: tarcieri

.typos.toml

@@ -1,10 +1,16 @@
 [files]
 extend-exclude = [
     ".git/",
-    "elliptic-curve/src/jwk.rs",
     "signature/tests/derive.rs"
 ]
 
+[default]
+extend-ignore-re = [
+    # Patterns which appear to be 36 or more characters of Base64/Base64url
+    '\b[0-9A-Za-z+/]{36,}\b',
+    '\b[0-9A-Za-z_-]{36,}\b',
+]
+
 [default.extend-words]
 # Authenticated Key Exchange
 "AKE" = "AKE"