feat: fix `annonate_base()` plus more modular approach to ph annotation

[markheckmann]

I suggest the below changes to ph annotation.

@davidgohel Please feel free to assign me the issue if you agree with the suggstions :)

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1) Fix annotate_base()

• currently outdated due to missing type index (e.g. body [3])
• index should be renamed id for coherent terminology across functions (see layout_properties, ph_location_id, etc.),
• positioning of layout and master name at top right could be more consistent
• ph visualization could be improved by adding a optional border line by default (+ more options)
• Some masters I work with have > 30 layouts. It would be good to have an arg to select a subset only

Currently

Missing type index (body[2]), index should be id, unclear which area phs span, misaligned master + layout.

New

2) More modular approach

Personally, I rarely use annotate_base() as it breaks my flow of working. Usually, I want to just quickly see a slide's phs directly. I found, however, that using an experimental phs_annotate() works well for me in conjunction with the recently added print(preview = TRUE) (PR #675)

read_pptx() |>
  add_slide("Title Slide") |>
  phs_annotate() |>  # annotate current slide's placeholders
  print(preview = TRUE)

I suggest these two new functions for a more modular approach ph annotatation:

phs_annotate():

• annotates the phs of one or more slide of the rpptx object
• more options: background color, border line, font size, keys, etc. (simple with feat: leverage unused dots in ph_with.* methods for modifying location / placeholder object #681)

add_annotated_layouts():

• adds one slide with annotated phs for each layout
• allows selecting of a subset of layouts only
• different from annotate_base() it is not yet written but only added to the rpptx object
• replaces the internals of annotate_base()

[davidgohel]

Thanks, this is an elegant suggestion !