Add missing properties for a dialog select element

[DominikPalo]

Summary

Some properties (data_source, selected_options, option_groups and min_query_length) were missing in definitions for a dialog select element.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #549 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #549   +/-   ##
=======================================
  Coverage   80.28%   80.28%           
=======================================
  Files           6        6           
  Lines         279      279           
  Branches       43       43           
=======================================
  Hits          224      224           
  Misses         38       38           
  Partials       17       17

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[aoberoi]

thanks @DominikPalo, this looks great to me.

@clavin, since you last edited these lines, thoughts?

[clavin]

Everything looks well and good to me. 👍✨ The only thoughts I have are completely related to #496.

[aoberoi]

awesome! since this is a step in the right direction for #496, i think it should be 👌 to merge.