Add option for specifying the capture attr on the file input

[carlobeltrame]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing (there aren't any, but I adapted the mock-data file)

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Reasoning

On mobile chat apps, it is very common nowadays to send photos which are captured directly in the app. In HTML5, we fortunately have the capture attribute on file inputs, which helps us acheive mostly the same user experience. When activating a file input with the capture attribute set to either true, "user" or "environment", the user gets the option to directly capture an image or video to populate the file input.

Other information:

[carlobeltrame]

@antoine92190 any input on this? Ideally I'd need this before the beginning of February, for a yearly event I'm writing the software for. Otherwise I'll have to keep my fork of this project as a git submodule in my project and keep transpiling it myself...

[antoine92190]

Look good, thanks

[carlobeltrame]

Thanks a lot for merging. Could you also publish a release? Otherwise I cannot use it (without publishing my own fork)

[antoine92190]

Done