adds some references

REFERENCES.md

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+Websites:
+    OSDev Wiki - https://wiki.osdev.org/
+    bona fide os developer - http://osdever.net/
+    LittleOSBook - https://littleosbook.github.io/
+    http://www.brokenthorn.com/Resources/OSDevIndex.html
+
+References:
+    NASM quick reference - https://www.posix.nl/linuxassembly/nasmdochtml/nasmdoca.html
+    ELF Reference - https://flint.cs.yale.edu/cs422/doc/ELF_Format.pdf
+    Anatomy of a program in memory - https://manybutfinite.com/post/anatomy-of-a-program-in-memory/
+    Linux Buddy System Paging - https://lwn.net/Articles/253361/