chore: Add missing #pragma once in header files

[kmichalikk]

Closes https://github.com/software-mansion/react-native-screens-labs/issues/587

Description

This PR adds missing #pragma once calls at the top of the header files for consistency.

Changes

Added #pragma once here and there.

Test code and steps to reproduce

Should be working exactly the same.

[t0maboro]

Note: I just checked the result with the script below, I didn't test the runtime

#!/bin/bash

SEARCH_DIR="."

find "$SEARCH_DIR" -type f \
    -name '*.h' \
    -not -path '*/node_modules/*' \
    -not -path '*/Pods/*' \
    -not -path '*/bundle/*' \
    -not -path '*/build/*' \
    -print0 | \
xargs -0 grep -L -i '#pragma once'

[kkafar]

Looks good!