Add release method which releases the sheet but not the data structure

[rubengees]

This is from a personal use case which I can imagine is also relevant for others.

In my application, I want to release the heavy sheet Bitmap after leaving the relevant Activity but keep the emoji datastructure in memory to still have good performance when opening the Activity again. When using the existing destroy method, I would have to install a provider each time the Activity is opened, which blocks the main thread and causes a visible stutter in my case. This new release method allows to release the Bitmap when leaving and still installing the Provider once in a central place.

[codecov]

Codecov Report

Merging #266 into master will increase coverage by 0.17%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #266      +/-   ##
==========================================
+ Coverage   28.48%   28.65%   +0.17%     
==========================================
  Files          22       22              
  Lines         825      827       +2     
  Branches       90       90              
==========================================
+ Hits          235      237       +2     
  Misses        571      571              
  Partials       19       19

Impacted Files	Coverage Δ
...c/main/java/com/vanniktech/emoji/EmojiManager.java	86.9% <100%> (+0.31%)	⬆️

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[vanniktech]

Can we add some javadoc?

[rubengees]

Sure! Give me a monent.

[rubengees]

Done!

[vanniktech]

Thanks once again :)