Printing: Add dimension information to greta array objects

``` r
library(greta)
#>
#> Attaching package: 'greta'
#> The following objects are masked from 'package:stats':
#>
#> binomial, cov2cor, poisson
#> The following objects are masked from 'package:base':
#>
#> %*%, apply, backsolve, beta, chol2inv, colMeans, colSums, diag,
#> eigen, forwardsolve, gamma, identity, rowMeans, rowSums, sweep,
#> tapply
# Could? say 1x1 matrix?
normal(0, 1)
#> ℹ Initialising python and checking dependencies, this may take a moment.
#> ✔ Initialising python and checking dependencies ... done!
#>
#> greta array
#> [,1]
#> [1,] ?
#>
# Could? say 10x1 matrix?
normal(0, 1, dim = 10)
#> greta array
#> [,1]
#> [1,] ?
#> [2,] ?
#> [3,] ?
#> [4,] ?
#> [5,] ?
#> [6,] ?
#> [7,] ?
#> [8,] ?
#> [9,] ?
#> [10,] ?
#>

# could say a 3x3 matrix?
wishart(df = 4, Sigma = diag(3))
#> greta array
#> [,1] [,2] [,3]
#> [1,] ? ? ?
#> [2,] 0 ? ?
#> [3,] 0 0 ?
#>
```

^{Created on 2024-08-13 with [reprex v2.1.1](https://reprex.tidyverse.org)}

Session info

``` r
sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#> setting value
#> version R version 4.4.1 Patched (2024-07-08 r86915)
#> os macOS Sonoma 14.5
#> system aarch64, darwin20
#> ui X11
#> language (EN)
#> collate en_US.UTF-8
#> ctype en_US.UTF-8
#> tz Australia/Hobart
#> date 2024-08-13
#> pandoc 3.2.1 @ /opt/homebrew/bin/ (via rmarkdown)
#>
#> ─ Packages ───────────────────────────────────────────────────────────────────
#> package * version date (UTC) lib source
#> base64enc 0.1-3 2015-07-28 [1] CRAN (R 4.4.0)
#> callr 3.7.6 2024-03-25 [1] CRAN (R 4.4.0)
#> cli 3.6.3 2024-06-21 [1] CRAN (R 4.4.0)
#> coda 0.19-4.1 2024-01-31 [1] CRAN (R 4.4.0)
#> codetools 0.2-20 2024-03-31 [2] CRAN (R 4.4.1)
#> crayon 1.5.3 2024-06-20 [1] CRAN (R 4.4.0)
#> digest 0.6.36 2024-06-23 [1] CRAN (R 4.4.0)
#> evaluate 0.24.0 2024-06-10 [1] CRAN (R 4.4.0)
#> fastmap 1.2.0 2024-05-15 [1] CRAN (R 4.4.0)
#> fs 1.6.4.9000 2024-06-26 [1] Github (r-lib/fs@714990b)
#> future 1.34.0 2024-07-29 [1] CRAN (R 4.4.0)
#> globals 0.16.3 2024-03-08 [1] CRAN (R 4.4.0)
#> glue 1.7.0 2024-01-09 [1] CRAN (R 4.4.0)
#> greta * 0.4.5.9000 2024-08-01 [1] local
#> hms 1.1.3 2023-03-21 [1] CRAN (R 4.4.0)
#> htmltools 0.5.8.1 2024-04-04 [1] CRAN (R 4.4.0)
#> jsonlite 1.8.8 2023-12-04 [1] CRAN (R 4.4.0)
#> knitr 1.48 2024-07-07 [1] CRAN (R 4.4.0)
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#> lifecycle 1.0.4 2023-11-07 [1] CRAN (R 4.4.0)
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#> magrittr 2.0.3 2022-03-30 [1] CRAN (R 4.4.0)
#> Matrix 1.7-0 2024-04-26 [2] CRAN (R 4.4.1)
#> parallelly 1.38.0 2024-07-27 [1] CRAN (R 4.4.0)
#> pkgconfig 2.0.3 2019-09-22 [1] CRAN (R 4.4.0)
#> png 0.1-8 2022-11-29 [1] CRAN (R 4.4.0)
#> prettyunits 1.2.0 2023-09-24 [1] CRAN (R 4.4.0)
#> processx 3.8.4 2024-03-16 [1] CRAN (R 4.4.0)
#> progress 1.2.3 2023-12-06 [1] CRAN (R 4.4.0)
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#> R6 2.5.1 2021-08-19 [1] CRAN (R 4.4.0)
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#> reprex 2.1.1 2024-07-06 [1] CRAN (R 4.4.0)
#> reticulate 1.38.0 2024-06-19 [1] CRAN (R 4.4.0)
#> rlang 1.1.4 2024-06-04 [1] CRAN (R 4.4.0)
#> rmarkdown 2.27 2024-05-17 [1] CRAN (R 4.4.0)
#> rstudioapi 0.16.0 2024-03-24 [1] CRAN (R 4.4.0)
#> sessioninfo 1.2.2 2021-12-06 [1] CRAN (R 4.4.0)
#> tensorflow 2.16.0 2024-04-15 [1] CRAN (R 4.4.0)
#> tfruns 1.5.3 2024-04-19 [1] CRAN (R 4.4.0)
#> vctrs 0.6.5 2023-12-01 [1] CRAN (R 4.4.0)
#> whisker 0.4.1 2022-12-05 [1] CRAN (R 4.4.0)
#> withr 3.0.1 2024-07-31 [1] CRAN (R 4.4.0)
#> xfun 0.46 2024-07-18 [1] CRAN (R 4.4.0)
#> yaml 2.3.10 2024-07-26 [1] CRAN (R 4.4.0)
#>
#> [1] /Users/nick/Library/R/arm64/4.4/library
#> [2] /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library
#>
#> ─ Python configuration ───────────────────────────────────────────────────────
#> python: /Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2/bin/python
#> libpython: /Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2/lib/libpython3.10.dylib
#> pythonhome: /Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2:/Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2
#> version: 3.10.14 | packaged by conda-forge | (main, Mar 20 2024, 12:51:49) [Clang 16.0.6 ]
#> numpy: /Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2/lib/python3.10/site-packages/numpy
#> numpy_version: 1.26.4
#> tensorflow: /Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2/lib/python3.10/site-packages/tensorflow
#>
#> NOTE: Python version was forced by use_python() function
#>
#> ──────────────────────────────────────────────────────────────────────────────
```