fix: placeholder and descriptions updated on the proposal template

[nathanbogale]

Description of Changes

• Added placeholders to each text field
• Added guidelines for each section to provide clear instructions.
• Updated description and guidance sections
• Improved formatting for readability.

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 443/443}$ | ${\color{red}Fail: 0/443}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 443/443}$ | ${\color{red}Fail: 0/443}$ |

[dtscalac]

LGTM

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 445/445}$ | ${\color{red}Fail: 0/445}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 445/445}$ | ${\color{red}Fail: 0/445}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 445/445}$ | ${\color{red}Fail: 0/445}$ |