Allowlist contributions and RIKEN-specific allowlist (#171)

* Update allowlist for intel 06_8F

* Add a folder for RIKEN under contribs, so we know which site the contributions are from.

* Add a readme for the contribs/ folder

* Update README.md

* Move the readme note for allowlist contribs to top-level readme, after Error and before msr_save

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Co-authored-by: francescoantici <francesco.antici98@gmail.com>

README.md

@@ -331,6 +331,11 @@ An individual operation requested a write to a read-only MSR.
 
 There are no msr_safe-specific error conditions.
 
+# ALLOWLIST CONTRIBUTIONS
+
+The contribs/ folder contains allowlists shared by 
+our external collaborators, organized by site-name.
+
 # msr-save
 
 The msrsave utility provides a mechanism for saving and restoring MSR values