Add support for textDocument/references for DTD

[angelozerr]

Fixes #234

Signed-off-by: azerr [email protected]

[NikolasKomonen]

@angelozerr If I try to peek a reference of a value that is not the definition I don't get any references.

eg:

<!ELEMENT font-fa|ce (X) > <-- peek references here gives the ATTLIST font-face reference
<!ATTLIST font-fa|ce >  <-- peek references here gives no references

Not sure if that is a design choice.

Otherwise, everything else works great.

[angelozerr]

<!ATTLIST font-face is linked to <!ELEMENT font-face (you can check that with definition on ATTLIST font-face. So if you find references from <!ELEMENT font-face you should see linked <!ATTLIST font-face.

Not sure if that is a design choice.

yes it's a choice, it's like references from java field.

[NikolasKomonen]

@angelozerr I understand that, but if I do peek definition on <!ATTLIST font-face> no options appear.

[angelozerr]

You should. If I test with svg.dtd, definition from <!ATTLIST font-face to <!ELEMENT font-face is working?

[angelozerr]

Thanks @NikolasKomonen for your review, please create an issue with missing feature.