Upgrade to latest handlebars.js (4.7.7)

[loganrosen]

Fixes #848. There's a critical vulnerability in handlebars.js < 4.7.7, so it's important that we upgrade the Java library/publish a new version as soon as possible.

mvn clean install succeeds.

[coveralls]

Coverage remained the same at 91.458% when pulling c21e68a on loganrosen:handlebars-4.7.7 into 1d44be3 on jknack:master.

[Sachpat]

Hi, can we have this merged soon and have the next version of handlebars which has updated handlebars.js? As our security scans continue to report CVE-2021-23369 against the latest version of handlebars.

[loganrosen]

@jknack Would you be able to merge this and cut a new version to address the security concerns?

[benwaxway]

What are the options, except building our own (really not wanted) to get out of this ? Won't also be unable to defer security for too long... Kinda worried as no new commit in more than a year... is it possible to reclaim the project or fork it and "declare" the fork new source of truth (a bit pushy maybe...;-))

[Sachpat]

Hi guys @jknack It would be really helpful if we merge this PR and release the new version soon. If needed I can offer some help regarding the same :) . As stated here #855 (comment), our security scans continue to report CVE-2021-23369 against the latest version of handlebars.

[Rob-Conan]

Can this MR be merged please? I have multiple security scans failing as a result of this issue.

[ghost]

Hi, another request for this to be merged. Our scans are currently reporting 4.7.6 as a vulnerability