Fix: Reattempt to initialise rg4js if a key is after a load has completed.

[Codex-]

PR to resolve #454

Reproduction of the issue: https://github.com/Codex-/rg4js-init-issue

Details of the issue: https://github.com/Codex-/rg4js-init-issue/tree/patch_test#rg4js-initialisation-issue-reproduction

I have tested this via a patch with logging on a branch which can be found here: https://github.com/Codex-/rg4js-init-issue/tree/patch_test

Logging output without fix:

raygun umd loaded
App raygun key has been set
App manual config slow started
raygun4js addEventListener load complete
raygun4js onLoadHandler <--------------------- init would happen here if the key was configured.
App manual config finished
App raygun key has been set
App raygun config run

Logging output with fix:

raygun umd loaded
App raygun key has been set
App manual config slow started
raygun4js addEventListener load complete
raygun4js onLoadHandler
raygun4js onLoadHandler hasCalledOnLoad true
App manual config finished
raygun4js hasCalledOnLoad true, calling onLoadHandler again...
raygun4js onLoadHandler <--------------------- init has happened now with a key set, huzzah!
raygun4js onLoadHandler hasCalledOnLoad true
App raygun key has been set
App raygun config run

Please let me know if you need any more details :)

[Deacon-McIntyre]

Thanks @Codex- - we're just testing this out on our end, looks good so far