Add unit= argument to body_add_gg, ... . Closes #626

[trekonom]

Hi David,

this PR adds a "unit=" argument to body_add_gg, ... thereby closing #626.

The reprex below shows that it (should) work:

library(officer)
library(ggplot2)

p <- ggplot(data = mtcars, aes(x = wt, y = mpg)) +
  geom_point()

doc <- read_docx()

doc <- body_add_gg(doc, p) # Works when unit is not set -> #323
doc <- body_add_gg(doc, p, unit = "in")
doc <- body_add_gg(doc, p, unit = "cm")
doc <- body_add_gg(doc, p, unit = "mm")

# In all 4 cases a plot is added with a width of 6 and height of 5 in units
# expressed by the unit argument

doc <- cursor_end(doc)
node <- docx_current_block_xml(doc)

.in_to_emu <- 914400; .cm_to_emu <- 360000; .mm_to_emu <- 36000

all(identical(
  as.numeric(xml2::xml_attr(xml2::xml_find_all(node, "//wp:extent"), "cx")) /
    c(.in_to_emu, .in_to_emu, .cm_to_emu, .mm_to_emu),
  rep(6, 4)
))
#> [1] TRUE

all(identical(
  as.numeric(xml2::xml_attr(xml2::xml_find_all(node, "//wp:extent"), "cy")) /
    c(.in_to_emu, .in_to_emu, .cm_to_emu, .mm_to_emu),
  rep(5, 4)
))
#> [1] TRUE

# Uses cli_abort for nice error messages

doc <- body_add_gg(doc, p, unit = "px")
#> Error in `check_unit()`:
#> ! `unit` should be one of in, cm, or mm.
#> ✖ `unit` was px".
doc <- body_add_gg(doc, p, unit = c("cm", "mm"))
#> Error in `check_unit()`:
#> ! `unit` is not length 1.
#> ✖ `unit` must be a string.
doc <- body_add_gg(doc, p, units = "cm")
#> Error in `body_add_gg()`:
#> ! Found a `units` argument. Did you mean `unit`?

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All modified and coverable lines are covered by tests ✅

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@@            Coverage Diff             @@
##           master     #628      +/-   ##
==========================================
+ Coverage   83.55%   85.90%   +2.34%     
==========================================
  Files          41       43       +2     
  Lines        5832     6967    +1135     
==========================================
+ Hits         4873     5985    +1112     
- Misses        959      982      +23     

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[davidgohel]

thanks a lot @trekonom and sorry for the delay