Support likert appearance

[florianm]

likert widget https://github.com/getodk/build2xlsform/blob/master/src/convert.ls#L64

[florianm]

Status quo on latest Build/build2xlsform master - kinda works although not explicitly supported.

Build @ https://github.com/getodk/build/commit/bf0f687535de7f75e78faf131e8772ec11af0a9e build2xlsform @ https://github.com/getodk/build2xlsform/commit/facbc1244b50cd94c068142434551d011ed6e41e

A simple Build form with two metadata fields (device ID and start geopoint) plus a choose one with likert appearance.

Sample forms: likert.zip

• 01 The ODK Build save file
• 02 Export as XML (appearance "likert" - lower case)
• 03 Export as XLSForm (appearance "Likert")
• 04 XLSForm converted with pyxform (xls2xform 03_27-likert.xlsx) and renamed with prefix 04

  Warnings:
  [row : 3] Question has no label: {'name': 'start_geopoint', 'type': 'start-geopoint'}
  Conversion complete!

• 04 passes ODK Validate java -jar odkvalidate.jar 04_27-likert.xml

Loading the direct XLSForm export into ODK Central v1.3 throws a warning about the missing language code. This issue is tracked at https://github.com/getodk/build/issues/260 but could be solved here in build2xlsform. Once the labels are corrected from label::English to label::English (en), the form uploads and renders in ODK Collect x2022.1.1 as likert widget. It seems the "likert" appearance is case insensitive and still works as appearance="Likert" because the XLSForm is converted (by Central's pyxform) and distributed to Collect as an XForm in the case insensitive format XML.

I still want to explicitly support the likert appearance with a translation of label "Likert" to value "likert" so that in future, Build could choose to change the label.