Add a few recent decisions into README.md

Forbid C++14 encroachment.
Add big-endian caveat.

Change-Id: I1059d3b23ada2d7db1b30ecf8a7c75b0f94e6b58
Reviewed-on: https://pdfium-review.googlesource.com/12311
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/README.md b/README.md
index 3c24b0c..6f80dc1 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,9 @@
 override the default value. If you specify Android build, the default CPU
 architecture will be "`arm`".
 
+It is expected that there are still some places lurking in the code which will
+not function properly on big-endian architectures. Bugs and/or patches are
+welcome, however providing this support is **not** a priority at this time.
 
 #### Google employees
 
@@ -171,5 +174,5 @@
 1. Code has to conform to the existing style and not Chromium/Google style.
 2. PDFium uses a different tool for code reviews, and credentials for
 the tool need to be generated before uploading a CL.
-
-
+3. PDFium is currently holding at C++11 compatibility, rejecting features that
+are only present in C++14 (onto which Chromium is now slowly moving).