Support rfc6570 uritemplates in click handler

[dschulten]

[Feature Request] – APIs can contain rfc6570 uritemplates, e.g. http://example.com{?personId*}. Building on #874, Insomnia should allow to provide uritemplate variables when the user clicks such a UriTemplate:

[dschulten]

Feature branch: https://github.com/dschulten/insomnia/tree/feature/follow-rfc6570-uritemplates

In uritemplates you can have composite values, e.g. lists or dictionaries. E.g. if personId is a list [123,456], then the template http://example.com{?personId*} expands to http://example.com?personId=123&personId=456. The same works for objects like {city: 'Newport Beach',state: 'CA'}.
We can allow users to edit such composite values in the multiline editor. When multiline is enabled, a button Click to edit allows to open the editor instead of an input field.

Uritemplate variables are a much wider concept than url query params, although there is some overlap. We therefore keep them separate from Request.params and use them only temporarily to build complete urls.

[gschier]

I like this! Nice work.

At first glance (just by the screenshot), it doesn't seem like this should depend on #874. Ideally it should be treated as completely separate and should even be able to be merged into the existing system of opening links in the browser.

Feel free to submit a PR for this, ideally without the included changes in #874