Fix Lua callback Vimscript calls, closes #181

[aweis89]

Title: Resolve Lua-Vimscript Callback Issues (#181)

Changes:

• Replaced vim.fn.tempname with os.tmpname() and vim.fn.writefile with custom Lua file writing function to fix E5560 errors.
• Ensured compatibility by adapting plugin functionalities to native Lua operations.

Motivation:
Addressed errors related to calling Vimscript functions from Lua callbacks, improving plugin stability and performance.

Testing:
Conducted manual tests to confirm correct behavior.

[deathbeam]

Made the fix as well in #182, would've waited if i knew someone else was fixing it but oh well, should be resolved now