Update EIP-5289: Use Base 64 (#5567)

EIPS/eip-5289.md

@@ -32,16 +32,67 @@ See [`IERC5289Library`](../assets/eip-5289/interfaces/IERC5289Library.sol).
 To request that certain documents be signed, revert with the following reason:
 
 ```solidity
-string.concat("5289:", libraryAddress1, "-", documentId1OfAddress1, "-", documentId2OfAddress1 ",", libraryAddress2, "-", documentId2, ...)
+string.concat("5289:", libraryAddress1, "-", documentId1OfAddress1, "-", documentId2OfAddress1 ",", libraryAddress2, "-", documentId1OfAddress2, ...)
 ```
 
-NOTE: If an address begins with one or more zeros, they may be omitted.
-NOTE 2: The document IDs are represented in hexadecimal.
+NOTE: If an address begins with one or more zeros, they may be omitted. Addresses are represented in base 64.
+NOTE 2: The document IDs are represented in base 64.
 
 Example:
 
 ```solidity
-"5289:0x1-1-2,0xdead-7b3"
+"5289:1-1-2,hEl/0-7bA"
+```
+
+#### Base 64
+
+From RFC 4648:
+
+```text
+                  Table 1: The Base 64 Alphabet
+
+ Value Encoding  Value Encoding  Value Encoding  Value Encoding
+     0 A            17 R            34 i            51 z
+     1 B            18 S            35 j            52 0
+     2 C            19 T            36 k            53 1
+     3 D            20 U            37 l            54 2
+     4 E            21 V            38 m            55 3
+     5 F            22 W            39 n            56 4
+     6 G            23 X            40 o            57 5
+     7 H            24 Y            41 p            58 6
+     8 I            25 Z            42 q            59 7
+     9 J            26 a            43 r            60 8
+    10 K            27 b            44 s            61 9
+    11 L            28 c            45 t            62 +
+    12 M            29 d            46 u            63 /
+    13 N            30 e            47 v
+    14 O            31 f            48 w         (pad) =
+    15 P            32 g            49 x
+    16 Q            33 h            50 y
+```
+
+NOTE: Padding is NOT used.
+
+Here is a TypeScript snippet to convert `Number` objects into base 64 strings and back.
+
+```typescript
+const digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/";
+
+function toB64(x: Number): string {
+    return x
+      .toString(2)
+      .split(/(?=(?:.{6})+(?!.))/g)
+      .map(bin => parseInt(bin, 2))
+      .map(digit => digits[digit])
+      .join("");
+}
+
+function fromB64(x: string): Number {
+    return Number.parseInt(
+      x.split("").reduce((bin, digit) => bin + new Number(digits.indexOf(digit)).toString(2).padStart(6, '0'), ""),
+      2
+    );
+}
 ```
 
 ### Signing a Document