Missing type coercion makes `npm run vscode:prepublish` fail

Line 99 in 894d09b

const parsedYAML = YAML.safeLoad(document.getText());

This line makes prepublish fail with:

$ npm run vscode:prepublish

> swagger-viewer@3.0.1 vscode:prepublish /home/matteo/temp/vs-swagger-viewer
> tsc -p ./

src/preview/client.ts:101:30 - error TS2339: Property 'swagger' does not exist on type 'string | object'.
  Property 'swagger' does not exist on type 'string'.

101               if (parsedYAML.swagger === "2.0") {
                                 ~~~~~~~

src/preview/client.ts:104:28 - error TS2339: Property 'openapi' does not exist on type 'string | object'.
  Property 'openapi' does not exist on type 'string'.

104                 parsedYAML.openapi &&
                               ~~~~~~~

src/preview/client.ts:105:28 - error TS2339: Property 'openapi' does not exist on type 'string | object'.
  Property 'openapi' does not exist on type 'string'.

105                 parsedYAML.openapi.match(/^3\.0\.\d(-.+)?$/)
                               ~~~~~~~

Found 3 errors.

An easy fix is to coerce this type to any. For instance: const parsedYAML = <any>YAML.safeLoad(document.getText());