Create and upload high res logo

[peterdesmet]

I created a new logo for git2data (in Photoshop):

• Table icon represents a (minimal) diff on a tabular data file, which is one of the goals of the package
• Table icon is inspired by font awesome, but created from scratch
• Red/green colours of table = git desktop colours to indicate git diff
• Pink of logo = INBO pink #c04384
• Font = Flanders Art Sans, also used for https://github.com/ropensci/wateRinfo/blob/master/man/figures/logo.png

Logo is the highest resolution I have (300dpi). I'm adding the high resolution version to the repo, so everyone has access to it. The file size (75kB) won't affect the display of the pkgdown website.

Note, to cleanup the repository, the sticker directory should probably be removed. This is not included in this PR.

[codecov-io]

Codecov Report

Merging #37 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #37   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          11     11           
  Lines         729    729           
=====================================
  Hits          729    729

Impacted Files	Coverage Δ
R/prune.R	100% <ø> (ø)	:arrow_up:

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[peterdesmet]

Can this PR be merged?