Updating placeholder to support html

[donatasj87]

This way you can pass a string to placeholder variable like "<b>Important!:</b>Please fill this field" and it would be properly rendered as html

[codecov]

Codecov Report

Merging #431 (3b8edbf) into master (f418683) will decrease coverage by 12.84%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #431       +/-   ##
==========================================
- Coverage   19.57%   6.73%   -12.85%     
==========================================
  Files           6       6               
  Lines         475     475               
  Branches      104     104               
==========================================
- Hits           93      32       -61     
- Misses        379     443       +64     
+ Partials        3       0        -3     

Impacted Files	Coverage Δ
...ar-editor/src/lib/ae-select/ae-select.component.ts	33.33% <0.00%> (-18.06%)	⬇️
...editor/src/lib/angular-editor-toolbar.component.ts	0.80% <0.00%> (-16.94%)	⬇️
...angular-editor/src/lib/angular-editor.component.ts	0.58% <0.00%> (-15.89%)	⬇️

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