feat(typescript): adds d.ts file

Fixes #7

index.d.ts

@@ -0,0 +1,51 @@
+export interface Rule {
+  subject: string | string[],
+  actions: string | string[],
+  conditions?: Object,
+  inverted?: boolean
+}
+
+export interface AbilityOptions {
+  subjectName: (subject: any) => string
+}
+
+export class Ability {
+  rules: Rule[]
+
+  static addAlias(alias: string, fields: string | string[]): void
+
+  constructor(rules?: Rule[], options?: AbilityOptions)
+
+  update(rules: Rule[]): Ability
+
+  can(action: string, subject: any): boolean
+
+  cannot(action: string, subject: any): boolean
+
+  rulesFor(action: string, subject: any): Rule[]
+
+  throwUnlessCan(action: string, subject: any): void
+}
+
+export abstract class AbilityBuilderParts {
+  rules: Rule[]
+
+  can(action: string | string[], subject: string | string[]): Rule
+
+  cannot(action: string | string[], subject: string | string[]): Rule
+}
+
+export class AbilityBuilder extends AbilityBuilderParts {
+  static define(params: AbilityOptions, dsl: Function): Ability
+  static define(dsl: Function): Ability
+
+  static extract(): AbilityBuilderParts
+}
+
+export class ForbiddenError extends Error {}
+
+export function rulesToQuery(rules: Rule[], convert: (rule: Rule) => Object): Object[] | null
+
+export function toMongoQuery(rules: Rule[]): Object[] | null
+
+export function mongoosePlugin(schema: any): any