Implement DocumentModel initialization

[gohabereg]

Changes

1. Update entities to accept serialized data into constructor — it enables model initialization using saved data
2. Update BlockNodeData structure to accept any object/array structures as Tool data
3. Update serialized data schema to mark ValueNode/TextNode data with special property $t
4. Add private initialize methods to EditorDocument and BlockNode classes to create entities from passed serialized data
5. Update ValueNode/TextNode methods call from BlockNode to support any tool data structure

Two issues raised to cover some of added code with integration tests: #40 #41

[github-actions]

✅ Mutation testing passed

Report: https://dashboard.stryker-mutator.io/reports/github.com/editor-js/document-model/PR-39

Mutated files

src/entities/BlockNode/consts.ts
src/entities/BlockNode/types/BlockChildType.ts
src/entities/EditorDocument/types/EditorDocumentSerialized.ts
src/entities/ValueNode/types/ValueSerialized.ts
src/utils/keypath.ts
src/utils/mapObject.ts
src/entities/BlockNode/index.ts
src/entities/BlockNode/types/BlockNodeConstructorParameters.ts
src/entities/BlockNode/types/BlockNodeData.ts
src/entities/BlockNode/types/BlockNodeSerialized.ts
src/entities/BlockNode/types/DataKey.ts
src/entities/BlockNode/types/index.ts
src/entities/BlockTune/index.ts
src/entities/BlockTune/types/BlockTuneConstructorParameters.ts
src/entities/BlockTune/types/BlockTuneSerialized.ts
src/entities/EditorDocument/index.ts
src/entities/EditorDocument/types/EditorDocumentConstructorParameters.ts
src/entities/EditorDocument/types/index.ts
src/entities/ValueNode/index.ts
src/entities/ValueNode/types/index.ts
src/entities/inline-fragments/InlineNode/index.ts
src/entities/inline-fragments/ParentInlineNode/index.ts
src/entities/inline-fragments/TextInlineNode/index.ts
src/entities/inline-fragments/TextNode/index.ts
src/tools/ToolsRegistry.ts
src/tools/types/BlockToolConstructable.ts
src/tools/types/index.ts
  

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	100%	468/468
🟢	Branches	99.21% (+0.19% 🔼)	126/127
🟢	Functions	99.23% (+0.09% 🔼)	129/130
🟢	Lines	100%	447/447

Show new covered files 🐣

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / BlockChildType.ts	100%	100%	100%	100%
🟢	... / index.ts	100%	100%	100%	100%
🟢	... / consts.ts	100%	100%	100%	100%
🟢	utils/keypath.ts	100%	100%	100%	100%
🟢	utils/mapObject.ts	100%	100%	100%	100%

Test suite run success

310 tests passing in 17 suites.

Report generated by 🧪jest coverage report action from 91b40ee

[neSpecc]

Could you please write a short changelog in the PR description? It helps with review