bigint: use native bigint instead of big-integer

To make it easier for our libraries to be used together, we are doing a
pass over them, standardizing on using native bigint for big numbers.
Nock-js already uses these. This library should follow.

This commit updates all aura-js library code to use native bigints, and
removed the big-integer dependency altogether.

README.md

@@ -6,19 +6,19 @@ This NPM package is intended to ease the flow of developing FE applications for
 
 ```typescript
 // @da manipulation
-function parseDa(da: string): BigInteger;
-function formatDa(da: BigInteger): string;
+function parseDa(da: string): bigint;
+function formatDa(da: bigint): string;
 // Given a bigint representing an urbit date, returns a unix timestamp.
-function daToUnix(da: BigInteger): number;
+function daToUnix(da: bigint): number;
 // Given a unix timestamp, returns a bigint representing an urbit date
-function unixToDa(unix: number): BigInteger;
+function unixToDa(unix: number): bigint;
 
 // @p manipulation
 // Convert a number to a @p-encoded string.
-function patp(arg: string | number | BigInteger): string;
+function patp(arg: string | number | bigint): string;
 function hex2patp(hex: string): string;
 function patp2hex(name: string): string;
-function patp2bn(name: string): BigInteger;
+function patp2bn(name: string): bigint;
 function patp2dec(name: string): string;
 // Determine the ship class of a @p value.
 function clan(who: string): string;
@@ -35,27 +35,27 @@ function cite(ship: string): string | null;
 
 // @q manipulation
 // Convert a number to a @q-encoded string.
-function patq(arg: string | number | BigInteger): string;
+function patq(arg: string | number | bigint): string;
 function hex2patq(arg: string): string;
 function patq2hex(name: string): string;
-function patq2bn(name: string): BigInteger;
+function patq2bn(name: string): bigint;
 function patq2dec(name: string): string;
 // Validate a @q string.
 function isValidPatq(str: string): boolean;
 // Equality comparison on @q values.
 function eqPatq(p: string, q: string): boolean;
 
 // @ud manipulation
-function parseUd(ud: string): BigInteger;
-function formatUd(ud: BigInteger): string;
+function parseUd(ud: string): bigint;
+function formatUd(ud: bigint): string;
 
 // @uv manipulation
-function parseUv(x: string): BigInteger;
-function formatUv(x: BigInteger | string): string;
+function parseUv(x: string): bigint;
+function formatUv(x: bigint | string): string;
 
 // @uw manipulation
-function parseUw(x: string): BigInteger;
-function formatUw(x: BigInteger | string): string;
+function parseUw(x: string): bigint;
+function formatUw(x: bigint | string): string;
 
 // @ux manipulation
 function parseUx(ux: string): string;

package.json

@@ -26,9 +26,6 @@
     "size": "size-limit",
     "analyze": "size-limit --why"
   },
-  "peerDependencies": {
-    "big-integer": "^1.6.51"
-  },
   "devDependencies": {
     "@size-limit/preset-small-lib": "^8.2.4",
     "@tsconfig/recommended": "^1.0.2",