feat(conventional-changelog-writer): writerOpts supports timeZone

[takuminish]

Hi there. I'm a user of this project.
Sorry... I use deepl because I am not good at English.

I've faced a problem that same as #594.

I created the PR because I thought it would be better to be able to set timeZone in writerOpts.

summary

add timezone option to writerOpts(#594 (comment))

The default value is 'UTC' to avoid breaking changes in the conventional-changelog-writer.

Usage

// option.js
export default {
    writerOpts: {
        timeZone: "Ameraica/Los_Angeles"
    }
}

$ conventional-changelog -p angular -i CHANGELOG.md -s  -n option.js

When a non-existent timezone is specified

When a non-existent timezone is specified, I get an error like the following.
Or should I catch the error?

// option.js
export default {
    writerOpts: {
        timeZone: "not_found"
    }
}

$ conventional-changelog -p angular -i CHANGELOG.md -s  -n option.js
RangeError: Invalid time zone specified: not_found
    at Intl.DateTimeFormat (<anonymous>)
    at dateFormatter...

If you like it, could you please review and merge this PR?
If further additional code or test is needed, we will accommodate.

[dangreen]

Thank you for the PR!

[coveralls]

coverage: 94.046% (+0.003%) from 94.043%
when pulling 5266d55 on takuminish:conventional-changelog-writer/add_timezone_option
into 7e51c6d on conventional-changelog:master.

[dangreen]

@takuminish Thanks!

[takuminish]

@dangreen Thanks for merging the PR!