Add block strings to GraphQL grammar

[pubmodmatt]

The GraphQL TextMate grammar did not have separate handling for block strings, which are different from normal string values in that they may contain unescaped characters like quotes. Block strings were matching the string.quoted.double.graphql scope, which did not handle these unescaped characters, leading to incorrect results:

A new string.quoted.triple.block.graphql scope is defined, which matches everything up to the closing """:

This becomes more important with Apollo Connectors, where the selection attribute is often a block string containing mapping selection syntax that may contain special characters.

[github-actions]

You can download the latest build of the extension for this PR here:
vscode-apollo-0.0.0-build-1740172715.pr-282.commit-3df2853.zip.

To install the extension, download the file, unzip it and install it in VS Code by selecting "Install from VSIX..." in the Extensions view.

Alternatively, run

code --install-extension vscode-apollo-0.0.0-build-1740172715.pr-282.commit-3df2853.vsix --force

from the command line.

For older builds, please see the edit history of this comment.