Document how to configure file associations for ZE data sets

[t1m0thyj]

Is your request for enhancement related to a problem? Please describe.

Currently we direct users to VS Code documentation about how to set up file associations, but in ZE V3 more detailed instructions are needed to define file associations that work for PDS members as well as sequential data sets.

Describe the solution you'd like

We should suggest to define wildcards in the format **/*COBOL*{,/*} as suggested by @traeok in zowe/zowe-explorer-vscode#3181 (comment):

Regarding the files.associations change in behavior: this is likely due to the change in path structure for PDS members. Before, we had inserted the member name into the file in parentheses (ex: TEST.COBOL(MEMB1)) vs. the new path structure TEST.COBOL/MEMB1. For v3, you'll need to adjust your associations so that they also support PDS members. Here are some example globs for reference:

**/*COBOL*{,/*} - matches /lpar.zosmf/TEST.COBOL.PS and /lpar.zosmf/TEST.COBOL.PDS/MEMBER
**/*JCL*{,/*} - matches /lpar.zosmf/TEST.JCL.PS and /lpar.zosmf/TEST.JCL.PDS/EXAMPLE

Related doc pages

https://docs.zowe.org/stable/user-guide/ze-usage-tips/#configure-the-detected-language-of-a-file-or-data-set

Additional context