docs: tabulate Linux user space memory maps

Will be useful for laying out the memory manager's memory maps.
Let's start with the x86_64 and AArch64 architectures.

documentation/linux/memory-map.md

@@ -0,0 +1,18 @@
+# Linux user space memory maps
+
+| Architecture |              Start | End                | Address space bits | Page size | Translation tables |
+| :----------: | -----------------: | :----------------- | :----------------: | :-------: | :----------------: |
+| `x86_64`     | `0000000000000000` | `00007fffffffffff` |         47         |    4 KB   |         4          |
+| `x86_64`     | `0000000000000000` | `00ffffffffffffff` |         56         |    4 KB   |         5          |
+| `arm64`      | `0000000000000000` | `0000007fffffffff` |         39         |    4 KB   |         3          |
+| `arm64`      | `0000000000000000` | `0000ffffffffffff` |         48         |    4 KB   |         4          |
+| `arm64`      | `0000000000000000` | `000003ffffffffff` |         42         |   64 KB   |         2          |
+| `arm64`      | `0000000000000000` | `000fffffffffffff` |         52         |   64 KB   |         3          |
+
+# References
+
+ - [`x86_64`][x86_64]
+ - [`arm64`][arm64]
+
+[x86_64]: https://www.kernel.org/doc/html/latest/arch/x86/x86_64/mm.html
+[arm64]: https://www.kernel.org/doc/html/latest/arch/arm64/memory.html