Add pli language

[1000TurquoisePogs]

Proposed changes

This PR adds a full PL/I language mode to the zlux-editor Monaco integration.

Changes:

• webClient/src/app/editor/code-editor/monaco/hiliters/pli.ts — new file containing:
  • PLI_HOVER_DOCS: ~120 entries covering statement and control-flow keywords (PROCEDURE, DO, IF, SELECT, DECLARE, ALLOCATE, ON, GET/PUT/READ/WRITE/OPEN/CLOSE, etc.), data type and variable attribute keywords (FIXED, FLOAT, BINARY, CHARACTER, POINTER, VARYING, BASED, CONTROLLED, EXTERNAL, etc.), ON condition names (ERROR, OVERFLOW, ENDFILE, ZERODIVIDE, CONVERSION, SUBSCRIPTRANGE, etc.), preprocessor directives (%INCLUDE, %IF, %DECLARE, %ACTIVATE, *PROCESS, etc.), and common built-in functions (SUBSTR, LENGTH, ADDR, NULL, ABS, INDEX, TRANSLATE, VERIFY, ONCODE, ONFILE, DATETIME, etc.).
  • PLI_HILITE: Monarch tokenizer (ignoreCase: true) with three keyword sets matched against identifiers:
    • keywords — statement/control-flow words → token pli-keyword (yellow bold)
    • attributes — data type and variable attributes → token pli-attribute (light blue)
    • builtins — built-in function names → token pli-builtin (green bold)
    • Additional tokenizer rules for block comments (/* ... */), line comments (//), % preprocessor directives, *PROCESS/*PROCINC compiler option records, single- and double-quoted string literals (with ''/"" escape handling and type suffix), numeric literals (integer, decimal, floating-point with exponent and type suffix), and operators/punctuation.
• webClient/src/app/editor/code-editor/monaco/monaco.config.ts — updated to:
  • Import PLI_HILITE and PLI_HOVER_DOCS from the new pli module.
  • Define PLI_LANG and register the language for extensions .pli, .pl1, .pli1.
  • Define and apply the pli-dark theme (yellow keywords, light-blue attributes, green builtins, amber preprocessor directives, white strings, orange numbers, red operators/punctuation).
  • Register a hover provider for the pli language that resolves identifiers against PLI_HOVER_DOCS and also handles %-prefixed preprocessor directives in the hover context.
• webClient/src/app/shared/editor-control/editor-control.service.ts — added case 'pli' to setThemeForLanguage() so the pli-dark theme activates automatically when a .pli or .pl1 file is opened.

Type of change

• New feature (non-breaking change which adds functionality)

PR Checklist

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes
• video or image is included if visual changes are made
• Relevant update to CHANGELOG.md
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works, or describe a test method below

Testing

1. Build the editor plugin and deploy to a Zowe Desktop instance.
2. Open a .pli or .pl1 file via the File Explorer. The editor should automatically apply the PL/I language mode and pli-dark theme.
3. Verify syntax highlighting for a typical PL/I source file:
   • Block comments (/* ... */) appear in cyan.
   • Line comments (//) appear in cyan.
   • Statement and control-flow keywords (PROCEDURE, DO, IF, SELECT, DECLARE, CALL, RETURN, ON, etc.) appear in yellow bold.
   • Data type and variable attribute words (FIXED, BINARY, CHARACTER, POINTER, VARYING, BASED, etc.) appear in light blue.
   • Built-in function names (SUBSTR, LENGTH, ADDR, NULL, ABS, etc.) appear in green bold.
   • Preprocessor directives (%INCLUDE, %IF, %DECLARE, *PROCESS) appear in amber bold with underline.
   • String literals ('...' and "...") appear in white; '' and "" escaped quotes are handled correctly.
   • Numeric literals (integers, decimals, and floats with exponents) appear in orange.
   • Operators and punctuation (;, ,, (, ), =, +, -, etc.) appear in red.
   • Unrecognized identifiers (variable names, structure tags, labels) receive no special coloring.
4. Hover over:
   • A statement keyword (PROCEDURE, DECLARE, DO, IF, ON, ALLOCATE, etc.) to see its hover tooltip.
   • A data attribute keyword (FIXED, CHARACTER, POINTER, VARYING, BASED, etc.) to see the tooltip.
   • A built-in function name (SUBSTR, ADDR, NULL, ONCODE, DATETIME) to see the tooltip.
   • An ON condition name (ERROR, ENDFILE, OVERFLOW, ZERODIVIDE) to see the tooltip.
   • A preprocessor directive word (e.g., position cursor on INCLUDE in a %INCLUDE line) to see the tooltip.
5. Manually switch the language mode to PL/I from the language picker and confirm it is listed as PL/I / PLI.
6. Verify .pl1 files are also detected automatically.