Awesome
<img src="https://github.com/ozgurgunes/Sketch-Case-Converter/blob/master/assets/icon.png?raw=true" alt="Sketch Case Converter" width="128" align="right" />Case Converter 
Case Converter plugin for Sketch, converts case of text in selected layers, symbol overrides or even all overrides of all instances of a symbol to Sentence case, Title Case, UPPER CASE or lower case.
Installation
Download the latest release, unzip and double click on the .sketchplugin file.
Alternatively
Search for Case Converter in Sketchrunner or Sketchpacks.
Usage
All plugin commands have 4 scopes depending on your selection.
Select Symbol Master
If you select a symbol master; first you will be asked to choose text overrides which which will be converted, then all chosen overrides of all instances of the symbol will be converted.
Select Symbol Instances
If you select instances of same symbol; like symbol master, first you will be asked to choose text overrides which which will be converted, then all chosen overrides of selected symbols will be converted.
Select Overrides
If you select overrides directly; all text overrides in your selection will be converted.
Select Text Layers
If your selection has any text layers; command will be applied on all text layers in your selection.
Settings
Plugin supports locale languages which mean you can convert istanbul to İSTANBUL if you choose "Turkish" in plugin settings.