fix!: no mixed receiver types (#23)

## Description

Currently, `bucket` and `Table` have mixed receiver types: some are pointer receviers, and others are value receivers.

As per the Go Wiki, [you can have value and pointer receivers, just don't mix them](https://go.dev/doc/faq#methods_on_values_or_pointers).

## Changes

- Replace all value receivers in `bucket` and `Table` with pointer receivers.

### Design Decisions

This decision was made due to the advice on the Go wiki.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #23
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

subtable.go

@@ -19,11 +19,11 @@ type subtable[K, V any] struct {
 
 // location determines where in the subtable a certain key would be placed. If
 // the capacity is 0, this will panic.
-func (t subtable[K, V]) location(key K) uint64 {
+func (t *subtable[K, V]) location(key K) uint64 {
 	return t.hash(key) % t.capacity
 }
 
-func (t subtable[K, V]) get(key K) (value V, found bool) {
+func (t *subtable[K, V]) get(key K) (value V, found bool) {
 	if t.capacity == 0 {
 		return
 	}
@@ -54,7 +54,7 @@ func (t *subtable[K, V]) resize(capacity uint64) {
 	t.size = 0
 }
 
-func (t subtable[K, V]) update(key K, value V) (updated bool) {
+func (t *subtable[K, V]) update(key K, value V) (updated bool) {
 	if t.capacity == 0 {
 		return
 	}