Add basic parser

[dirkgroot]

Add a very simple parser, which should provide just enough of a basis to add basic editor functionality like code formatting and auto indentation.

[codecov]

Codecov Report

Merging #34 (c01d377) into main (05ac0fc) will increase coverage by 22.44%.
The diff coverage is 64.02%.

@@             Coverage Diff             @@
##             main      #34       +/-   ##
===========================================
+ Coverage   36.20%   58.64%   +22.44%     
===========================================
  Files          15       29       +14     
  Lines         232      636      +404     
  Branches        3      199      +196     
===========================================
+ Hits           84      373      +289     
- Misses        148      194       +46     
- Partials        0       69       +69     

Impacted Files	Coverage Δ
...en/nl/dirkgroot/structurizr/dsl/psi/SDVisitor.java	0.00% <0.00%> (ø)
...groot/structurizr/dsl/psi/impl/SDArgumentImpl.java	25.00% <0.00%> (ø)
...structurizr/dsl/psi/impl/SDBlockStatementImpl.java	7.14% <7.14%> (ø)
...turizr/dsl/psi/impl/SDSingleLineStatementImpl.java	14.28% <14.28%> (ø)
...urizr/dsl/psi/impl/SDExplicitRelationshipImpl.java	16.66% <16.66%> (ø)
...urizr/dsl/psi/impl/SDImplicitRelationshipImpl.java	16.66% <16.66%> (ø)
...t/structurizr/dsl/psi/impl/SDKeyValuePairImpl.java	16.66% <16.66%> (ø)
...izr/dsl/psi/impl/SDPropertyBlockStatementImpl.java	16.66% <16.66%> (ø)
...ot/structurizr/dsl/psi/impl/SDScriptBlockImpl.java	16.66% <16.66%> (ø)
...urizr/dsl/psi/impl/SDIdentifierReferencesImpl.java	20.00% <20.00%> (ø)
... and 8 more

... and 3 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more