Added a sample for custom events

[pavelgj]

No description provided.

[egilmorez]

Thanks Pavel!

[jhuleatt]

Thank you @pavelgj! The sample itself looks good to me, just two requests:

1. Please target this PR against the gen2 branch and move it to the 2nd-gen folder. You can use this PR: #968 as a template

2. Please add a brief README. You can use this as a template:

Firebase Custom Events sample ================================================ (short description) Getting Started --------------- (install the resize-images extension, deploy the function, etc) License ------- © Google, 2022. Licensed under an [Apache-2](../../../LICENSE) license.

[egilmorez]

Thanks Pavel! This works for me as/is with the two snippet blocks.

As shown in our internal draft, this means hard-coding the non-default example, but that's OK with me if it's OK with Jeff.

[jhuleatt]

Thanks Pavel! This works for me as/is with the two snippet blocks.

As shown in our internal draft, this means hard-coding the non-default example, but that's OK with me if it's OK with Jeff.

Since all that changes are the options passed to the functions, I think it's ok to hard-code.

[jhuleatt]

Since @egilmorez and I have approved and @peterfriese's comment is addressed, I'm going to merge this. Thank you Pavel!!