PropTypes.exact descriptions flow oddly in some R package docs

[rpkyle]

As @shammamah noted in plotly/dash-bio#382, the flow of description strings is somewhat odd. Example: the dashbioCircos.Rd file contains the following information for layout:

\item{layout}{List of lists containing elements 'len', 'color', 'label', 'id'.
those elements have the following types:
  - len (numeric; required): the length of the block.
  - color (character; required): the color of the block.
  - label (character; required): the labels of the block.
  - id (character; required): the id of the block, where it will recieve
data from the specified "track" id.s. The overall layout of the Circos graph, provided
as a list of dictionaries.}

Ideally, the line

The overall layout of the Circos graph, provided as a list of dictionaries.

should follow

List of lists containing elements 'len', 'color', 'label', 'id'.

The R package generation code should be modified to more elegantly handle these descriptions. This may require slightly rewording/modifying the line those elements have the following types.

@alexcjohnson

[alexcjohnson]

There's also "id.s" ie an errant plural. That part at least was already fixed on the Python side, I believe... which makes me think we have an opportunity to share code - we should only have one routine constructing these blocks, that just has separate specific type conversions for the different languages.

[gvwilson]

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