feat(extended_json): EJSON.to/fromBuffer

[spal1]

NODE-2008

Two methods are being added to bson.EJSON: toBuffer(str) and fromBuffer(buffer)

[jimmywarting]

Hmm, this did go a tiny bit about my recommendation about stop depending on buffer and making bson more cross friendlier for both deno and browsers.
if anything then i think you should have to/from uint8array or ArrayBuffer

[bajanam]

Thank you for submitting this PR! While our current development plan is at capacity, we will track this in Jira for future prioritization.