Fix wording and format of CLI help text

[cuminandpaprika]

Fixes inconsistent capitalisation for CLI help text

Flags:
      --help                 Show context-sensitive help (also try --help-long and --help-man).
      --plantuml=PLANTUML    plantuml service to use
  -p, --port=":6900"         Port to serve on
      --type="markdown"      Type of output
  -o, --output=OUTPUT        OutputDir directory to generate to
  -v, --verbose              Verbose logs
      --templates=TEMPLATES  custom templates to use, separated by a comma
      --outputFileName=""    output file name for pages; {{.Title}}
      --serve                Start a http server and preview documentation
      --noCSS                disable adding css to served html
      --disableLiveReload    disable live reload
      --noImages             don't create images
      --embed                Embed images instead of creating svgs
      --mermaid              use mermaid diagrams where possible
      --redoc                generate redoc for specs imported from openapi. Must be run on a git repo.
      --imageDest=IMAGEDEST  Optional image directory destination (can be outside output)

Args:
  <input>  input sysl file to generate documentation for

After

usage: sysl-catalog [<flags>] <input>

Flags:
      --help                 Show context-sensitive help (also try --help-long and --help-man).
      --plantuml=PLANTUML    Plantuml service to use
  -p, --port=":6900"         Port to serve on
      --type="markdown"      Type of output
  -o, --output=OUTPUT        OutputDir directory to generate to
  -v, --verbose              Verbose logs
      --templates=TEMPLATES  Custom templates to use, separated by a comma
      --outputFileName=""    Output file name for pages; {{.Title}}
      --serve                Start a http server and preview documentation
      --noCSS                Disable adding css to served html
      --disableLiveReload    Disable live reload
      --noImages             Disable image generation
      --embed                Embed images instead of creating svgs
      --mermaid              Enable mermaid for diagram generation instead of Plantuml (Not currently supported)
      --redoc                Enable Redoc generation for specs imported from OpenAPI. Must be run on a git repo.
      --imageDest=IMAGEDEST  Optional image directory destination (can be outside of the path provided using --output)

Args:
  <input>  Input sysl file to generate documentation for

Checklist:

• [ ] Added tests
• [ ] Updated documentation