chore(v2): replace wait-file with wait-on to reduce npm warnings

[lex111]

Motivation

I couldn't figure out the reason why wait-on was not originally used, but we can probably safely replace wait-file with it (these libs has same interface). This way we will reduce the number of npm warnings on install deps (because wait-file is using hapi/joi, which was moved to another place):

npm WARN deprecated core-js@2.6.11: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
- npm WARN deprecated @hapi/joi@15.1.1: Switch to 'npm install joi'
npm WARN deprecated chokidar@2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
- npm WARN deprecated @hapi/hoek@8.5.1: This version has been deprecated and is no longer supported or maintained
- npm WARN deprecated @hapi/topo@3.1.6: This version has been deprecated and is no longer supported or maintained
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
- npm WARN deprecated @hapi/address@2.1.4: Moved to 'npm install @sideway/address'
- npm WARN deprecated @hapi/bourne@1.3.2: This version has been deprecated and is no longer supported or maintained
npm WARN deprecated core-js@1.2.7: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

See logs for E2E test for v2.

Related PRs

(If this PR adds or changes functionality, please take some time to update the docs at https://github.com/facebook/docusaurus, and link to your PR here.)

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Filename	Size	Change
website/build/blog/2017/12/14/introducing-docusaurus/index.html	20.7 kB	0 B
website/build/docs/introduction/index.html	180 B	0 B
website/build/index.html	5.84 kB	+1 B
website/build/main.********.js	108 kB	0 B
website/build/styles.********.css	17.4 kB	0 B

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